It doesn't matter how good the password is on your computer if you forget to lock the machine when you step away. A lot of people set up secure passwords to lock their machines and keep people from being able to access their computer without their knowledge. Many of these same people have their machines set to lock 10-15 minutes after the last activity.
That means if you are done using your machine and simply leave with it still running, there is a big window where folks can walk up and use your computer. An interesting product is on Kickstarter called the GateKeeper. This device has two purposes. The first is that it can act as a Bluetooth tracker to help you keep up with your stuff.
The second use for the GateKeeper is that it can be used as a proximity lock for your PC. With the GateKeeper, when you walk away from your Mac or Windows computer it will automatically lock. That means no window of opportunity before Windows locks itself down.
In addition to being a proximity lock for your computer, it can also be used like a normal Bluetooth tracking device. It can alarm if you walk away from your smartphone or computer. It can also be attached to a purse or backpack and alarm if you walk away from it. The device was seeking $12,000 on Kickstarter and has raised over $31,000 so far with a bit more than two days to go at the time of writing.