Android (rooted): NFC is awesome. It lets you automate your phone for every room in the house, running any task you can imagine when you place your phone on a tag. With the help of this hack, you can make NFC twice as useful by having it run an action when you remove your phone from a tag as well.
This hack solves a big annoyance with NFC. Normally, you can change a setting when you tap your phone to a tag, but you can't revert it back to default when you remove it. Now you can: For example, you can set your phone to silent when you place it on your dresser and turn the sound back on when you remove it. You could turn on Bluetooth when you place your phone in your car dock, and turn it off when you remove it.
You'll need a few different APKs to get the job done, and you'll need to work with Tasker, but the results are pretty cool. Check out the video above for an example, and hit the link below for the instructions.