[Recoil42]

Android already does this. It's called Smart Lock. Just set your computer as a trusted device:

https://support.google.com/nexus/answer/6093922?hl=en-CA

[pathikrit]

No it doesn't. You can't unlock your Mac with your Android whereas there are plenty of apps that can do that from your iPhone:

http://macid.co/

http://www.knocktounlock.com/

http://www.fingerkeyapp.com/

http://www.appuous.com/products/mac/keycard.html

[smellf]

It looks like the Lollipop Smart Lock can unlock your phone when it's in proximity to your PC, whereas nearlock will unlock your PC when it's in proximity to your phone.

[AdmiralAsshat]

This feature is only available within Android 5.0, however, and the pool of devices running Lollipop at the moment is pretty much limited to the Nexus line.

[zarriak]

Although it is only available on Lollipop, I find it pretty neat that these features have native support. The caveat about setting a trusted place to unlock is straight out of Tomorrow Never Dies[0]:

"Be aware that location signals can be replicated or manipulated — someone with access to specialised equipment could unlock your device."

[0]: http://en.wikipedia.org/wiki/Tomorrow_Never_Dies