Ignore No More
The Ignore No More application on Android (soon to be on iOS) has created quite a buzz today. Simply put, a parent may lock their children's phone until it is unlocked by the parent on their phone or the parent gives them a temporary unlocking password. This is one way a mother is going about to parenting (rebellious teens) in this age of cell phones; basically, contact the parent or else you don't get to use your phone.
While this application is advertised for the parent to install on their children's phone, there is nothing stopping more technologically-able teens from installing it on their parents' phone (e.g. while "helping" them figure something out). The child told pretend to be the parent! As a result, I think this portion of the app's site is false:

In an ideal world, this application would be perfect for parenting. (Well, perfect parenting would deem this application completely useless)
But let's take this outside the parent/child relationship and pose it in a romantic or just friendly relationship. It would awful for someone to install it on another's phone without their permission. It can be easily used in an ill-advised manner. Imagine how it could be used while a couple is in a dispute...
Quite the interesting application by the mother though!