To obtain the magnetic stripe data from your card, you will need a reader. In the US, they are available on both Amazon and Ebay for around $20 delivered. The inexpensive ones are USB devices that act as keyboard input, so no special drivers are needed on Windows or Mac OS X computers. While I'm sure there's more secure options, you can use an app like Google Keep to quickly transfer the swipe input to your phone and paste it into the app. The card data entered into the app is stored using Android's SharedPreference API in a way that is not accessible by other apps on a non-rooted phone.
The full source code to SwipeYours is available on Github: https://github.com/dimalinux/SwipeYours
Blog describing many details of SwipeYours: http://blog.simplytapp.com/2014/01/host-card-emulation-series-swipeyours.html
SwipeYours requires both NFC and Android 4.4 (KitKat) or newer for HCE (Host Card Emulation).
Privacy: This app has no Internet permissions and will not transfer your card information anywhere other than over the NFC interface for payments.
Many traffic lights all over the US are equipped with a system to let emergency vehicles override the normal light sequence. You may have heard that you can trigger these lights by flashing your brights, but that doesn't really work. The frequency that the light sensor is sensitive to is far too fast to trigger manually.
Enter RedLight GreenLight.
Show off to your friends. Amaze yourself. Make your red light waits a lot more enjoyable.
Here's how it works:
Just press the "Flash it!" button on the bottom of the screen, then turn your phone screen towards the traffic light. The program counts down for 3 seconds, then begins to flash a code. Not all sensors work the same way and RedLight GreenLight may not be effective in all situations.
Use at your own risk. Do not use where prohibited by law. For novelty purposes only.