I talked to a lawyer for similar reasons (someone used my name on a different platform). Given the popularity of your app, if the other guy hasn't been using this name before, you have a very clear case even without a trademark. But it costs money. A C&D letter can easily be $1000 and if the copycat doesn't cough up the money, you will have to pay the lawyer.
But I would send a strongly worded letter to the developer first. Here's the thing though: While the law is clearly on your side (that's what my lawyer said), it is a whole different story to recover the money. If he doesn't pay after the C&D, you need to go to court and things become expensive then. Martin Gentle Alarm -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en