I'm Getting Arrested is an app that was created after its developer was arrested for civil disobedience. Here's the description from CNET:
It lets you quickly notify your family, friends, and crack legal team (if you have one) of your situation with a single tap of your finger. Just initially enter a custom message and some SMS-ready numbers to contact in the event of your arrest. Then, as you're about to be corralled into the back of a squad car, fire the app up and long-press the bull's-eye for 2 seconds. From there, you can rest assured that your message will be sent to the appropriate contacts.
Sorry, iPhone users, the app is Android-only right now.