<s>
An	O
activity	B-Device
tracker	I-Device
,	O
also	O
known	O
as	O
a	O
fitness	B-Device
tracker	I-Device
,	O
is	O
a	O
device	O
or	O
application	O
for	O
monitoring	O
and	O
tracking	O
fitness-related	O
metrics	O
such	O
as	O
distance	O
walked	O
or	O
run	O
,	O
calorie	O
consumption	O
,	O
and	O
in	O
some	O
cases	O
heartbeat	O
.	O
</s>
<s>
It	O
is	O
a	O
type	O
of	O
wearable	B-Operating_System
computer	I-Operating_System
.	O
</s>
<s>
The	O
term	O
is	O
now	O
primarily	O
used	O
for	O
smartwatches	B-Application
that	O
are	O
synced	B-Application
,	O
in	O
many	O
cases	O
wirelessly	O
,	O
to	O
a	O
computer	O
or	O
smartphone	B-Application
for	O
long-term	O
data	O
tracking	O
.	O
</s>
<s>
There	O
are	O
also	O
independent	O
mobile	B-Application
and	O
Facebook	O
apps	O
.	O
</s>
<s>
The	O
term	O
"	O
activity	B-Device
trackers	I-Device
"	O
now	O
primarily	O
refers	O
to	O
wearable	B-Operating_System
devices	O
that	O
monitor	O
and	O
record	O
a	O
person	O
's	O
fitness	O
activity	O
.	O
</s>
<s>
Wearable	B-Operating_System
heart	O
rate	O
monitors	O
for	O
athletes	O
were	O
available	O
in	O
1981	O
.	O
</s>
<s>
Wearable	B-Operating_System
fitness	B-Device
tracking	I-Device
devices	O
,	O
including	O
wireless	O
heart	O
rate	O
monitoring	O
that	O
integrated	O
with	O
commercial-grade	O
fitness	O
equipment	O
found	O
in	O
gyms	O
,	O
were	O
available	O
in	O
consumer-grade	O
electronics	O
by	O
at	O
least	O
the	O
early	O
2000s	O
.	O
</s>
<s>
Electronic	O
activity	B-Device
trackers	I-Device
are	O
fundamentally	O
upgraded	O
versions	O
of	O
pedometers	O
;	O
in	O
addition	O
to	O
counting	O
steps	O
,	O
they	O
use	O
accelerometers	O
and	O
altimeters	O
to	O
calculate	O
mileage	O
,	O
graph	O
overall	O
physical	O
activity	O
,	O
calculate	O
calorie	O
expenditure	O
,	O
and	O
in	O
some	O
cases	O
also	O
monitor	O
and	O
graph	O
heart	O
rate	O
and	O
quality	O
of	O
sleep	O
.	O
</s>
<s>
Early	O
versions	O
such	O
as	O
the	O
original	O
Fitbit	B-Application
(	O
2009	O
)	O
,	O
were	O
worn	O
clipped	O
to	O
the	O
waist	O
;	O
formats	O
have	O
since	O
diversified	O
to	O
include	O
wristbands	O
and	O
armbands	O
(	O
smart	B-Device
bands	I-Device
)	O
and	O
smaller	O
devices	O
that	O
can	O
be	O
clipped	O
wherever	O
preferred	O
.	O
</s>
<s>
Apple	O
and	O
Nike	O
together	O
developed	O
the	O
Nike+iPod	B-Application
,	O
a	O
sensor-equipped	O
shoe	O
that	O
worked	O
with	O
an	O
iPod	B-Device
Nano	I-Device
.	O
</s>
<s>
In	O
addition	O
,	O
logging	O
apps	O
exist	O
for	O
smartphones	B-Application
and	O
Facebook	O
;	O
the	O
Nike+	B-Application
system	O
now	O
works	O
without	O
the	O
shoe	O
sensor	O
,	O
through	O
the	O
GPS	O
unit	O
in	O
the	O
phone	O
.	O
</s>
<s>
The	O
Apple	B-Device
Watch	I-Device
and	O
some	O
other	O
smart	B-Application
watches	I-Application
offer	O
fitness	B-Device
tracker	I-Device
functions	O
.	O
</s>
<s>
In	O
the	O
US	O
,	O
BodyMedia	B-Device
has	O
developed	O
a	O
disposable	O
activity	B-Device
tracker	I-Device
to	O
be	O
worn	O
for	O
a	O
week	O
,	O
which	O
is	O
aimed	O
at	O
medical	O
and	O
insurance	O
providers	O
and	O
employers	O
seeking	O
to	O
measure	O
employees	O
 '	O
fitness	O
,	O
and	O
Jawbone	O
's	O
UP	O
for	O
Groups	O
aggregates	O
and	O
anonymizes	O
data	O
from	O
the	O
company	O
's	O
wearable	B-Operating_System
activity	B-Device
trackers	I-Device
and	O
apps	O
for	O
employers	O
.	O
</s>
<s>
Other	O
activity	B-Device
trackers	I-Device
are	O
intended	O
to	O
monitor	O
vital	O
signs	O
in	O
the	O
elderly	O
,	O
epileptics	O
,	O
and	O
people	O
with	O
sleep	O
disorders	O
and	O
alert	O
a	O
caregiver	O
to	O
a	O
problem	O
.	O
</s>
<s>
Earbuds	O
and	O
headphones	B-Device
are	O
a	O
better	O
location	O
for	O
measuring	O
some	O
data	O
,	O
including	O
core	O
body	O
temperature	O
;	O
Valencell	B-Device
has	O
developed	O
sensor	O
technology	O
for	O
new	O
activity	B-Device
trackers	I-Device
that	O
take	O
their	O
readings	O
at	O
the	O
ear	O
rather	O
than	O
the	O
wrist	O
,	O
arm	O
,	O
or	O
waist	O
.	O
</s>
<s>
There	O
are	O
collar-mounted	O
activity	B-Device
trackers	I-Device
for	O
dogs	O
.	O
</s>
<s>
Much	O
of	O
the	O
appeal	O
of	O
activity	B-Device
trackers	I-Device
that	O
makes	O
them	O
effective	O
tools	O
in	O
increasing	O
personal	O
fitness	O
comes	O
from	O
their	O
making	O
it	O
into	O
a	O
game	O
,	O
and	O
from	O
the	O
social	O
dimension	O
of	O
sharing	O
via	O
social	O
media	O
and	O
resulting	O
rivalry	O
.	O
</s>
<s>
The	O
standard	O
activity-tracking	O
smartphone	B-Application
or	O
web	O
apps	O
present	O
data	O
in	O
statistical	O
form	O
meant	O
to	O
be	O
viewed	O
after	O
the	O
activity	O
has	O
ended	O
.	O
</s>
<s>
Social	O
networks	O
associated	O
with	O
activity	B-Device
trackers	I-Device
have	O
led	O
to	O
breaches	O
of	O
privacy	O
such	O
as	O
involuntary	O
publication	O
of	O
sexual	O
activity	O
,	O
and	O
the	O
potential	O
for	O
advertisers	O
and	O
health	O
insurers	O
to	O
access	O
private	O
health	O
data	O
through	O
the	O
devices	O
is	O
a	O
concern	O
.	O
</s>
<s>
In	O
2016	O
,	O
there	O
were	O
several	O
advances	O
made	O
in	O
regard	O
to	O
fitness	B-Device
tracking	I-Device
geared	O
toward	O
kids	O
with	O
a	O
variety	O
of	O
options	O
from	O
organizations	O
such	O
as	O
UNICEF	O
and	O
Garmin	O
.	O
</s>
<s>
Wearable	B-Operating_System
sensors	O
have	O
been	O
widely	O
used	O
in	O
medical	O
sciences	O
,	O
sports	O
and	O
security	O
.	O
</s>
<s>
Wearable	B-Operating_System
sensors	O
can	O
detect	O
abnormal	O
and	O
unforeseen	O
situations	O
,	O
and	O
monitor	O
physiological	O
parameters	O
and	O
symptoms	O
through	O
these	O
trackers	O
.	O
</s>
<s>
Moreover	O
,	O
in	O
sports	O
training	O
there	O
is	O
an	O
increasing	O
demand	O
for	O
wearable	B-Operating_System
sensors	O
.	O
</s>
<s>
For	O
example	O
,	O
measurement	O
of	O
sweat	O
rate	O
was	O
possible	O
only	O
in	O
laboratory	O
based	O
systems	O
a	O
few	O
years	O
ago	O
,	O
but	O
is	O
now	O
possible	O
using	O
wearable	B-Operating_System
sensors	O
.	O
</s>
<s>
Activity	B-Device
trackers	I-Device
are	O
available	O
both	O
with	O
and	O
without	O
display	O
.	O
</s>
<s>
Certain	O
movements	O
of	O
the	O
user	O
,	O
such	O
as	O
working	O
in	O
the	O
household	O
,	O
cycling	O
,	O
swimming	O
,	O
dancing	O
or	O
rowing	O
can	O
distort	O
the	O
results	O
obtained	O
from	O
activity	B-Device
trackers	I-Device
.	O
</s>
<s>
The	O
connection	O
of	O
activity	B-Device
trackers	I-Device
with	O
social	O
networks	O
can	O
lead	O
to	O
violation	O
of	O
privacy	O
,	O
such	O
as	O
involuntary	O
publication	O
of	O
sexual	O
activity	O
.	O
</s>
<s>
The	O
apps	O
of	O
some	O
activity	B-Device
trackers	I-Device
not	O
only	O
transmit	O
personal	O
data	O
,	O
but	O
also	O
private	O
address	O
lists	O
to	O
servers	O
on	O
the	O
Internet	O
without	O
notifying	O
or	O
asking	O
the	O
user	O
.	O
</s>
<s>
However	O
,	O
the	O
results	O
of	O
a	O
study	O
among	O
semi-professional	O
(	O
half	O
-	O
)	O
marathon	B-Application
participants	O
suggests	O
that	O
these	O
users	O
are	O
open	O
towards	O
sharing	O
tracked	O
activity	O
data	O
on	O
a	O
voluntary	O
basis	O
with	O
:	O
friends	O
(	O
51.7	O
%	O
)	O
,	O
family	O
members	O
(	O
43.4	O
%	O
)	O
,	O
or	O
a	O
physician	O
(	O
32.3	O
%	O
)	O
.	O
</s>
<s>
However	O
,	O
it	O
has	O
been	O
noted	O
that	O
the	O
activity	B-Device
tracker	I-Device
used	O
in	O
this	O
study	O
is	O
a	O
now-discontinued	O
model	O
that	O
is	O
worn	O
on	O
the	O
upper	O
arm	O
,	O
which	O
might	O
be	O
uncomfortable	O
,	O
and	O
wear	O
times	O
of	O
the	O
tracker	O
were	O
low	O
.	O
</s>
<s>
One	O
review	O
of	O
six	O
studies	O
found	O
that	O
there	O
was	O
little	O
evidence	O
that	O
activity	B-Device
trackers	I-Device
improve	O
health	O
outcomes	O
.	O
</s>
<s>
Another	O
systematic	O
review	O
covering	O
35	O
studies	O
and	O
7454	O
participants	O
,	O
published	O
at	O
the	O
British	O
Journal	O
of	O
Sports	O
Medicine	O
,	O
found	O
that	O
activity	B-Device
trackers	I-Device
increased	O
people	O
's	O
physical	O
activity	O
by	O
an	O
average	O
of	O
1850	O
steps/day	O
.	O
</s>
