With the rise in anti-immigrant laws in the wake of Arizona's SB1070, immigrants and their advocates are concerned about widespread racial profiling during traffic stops and police officers attempting to enforce immigration law by stopping people just to check for their "papers."
When we hear stories of this type of unconstitutional law enforcement behavior, however, it is often a "he said, she said" situation in which the immigrant reports being harassed or asked for their "papers" and the officer saying they did nothing of the sort. Also, the length of time that someone is detained in order to check their immigration status is often in dispute, again with the immigrant stating one length of time and the officer saying it was much shorter.
It would be nice to use technology--perhaps again using a phone's GPS data--to be able to discern how long someone was stopped by the police, and perhaps use the phone's voice memo functions to record conversations between the officer and the person being detained in order to get "neutral" evidence of what exactly was said and asked for by the officer. Combining this in one easy to use app would be interesting and help provide immigrants with a way to prove their case and protect themselves from over-reaching by law enforcement.