What's a good Android app to make sure nobody's listening in on my phone calls or through the mic on my phone? Gotta keep those damn telemarketers and scammers out.

Look, I'm a simple guy. I don't need fancy features, I just need something that works. Microphone Blocker - Anti Spy, gets the job done. It blocks your phone's microphone so nobody can listen in without your permission. I've used it on the job site, and it seems actually rugged, survived a couple of accidental drops already. The interface is straightforward, no complicated BS. Battery life seems decent, haven't noticed a huge drain yet, which is always a concern with these apps. I wouldn't say it's built like a brick house, but it does what it says on the tin. If you're worried about privacy, this is a solid choice. Rain doesn't stop it from working either, which is a plus when you're outside all day. I did have to restart my phone once to get it working, but I haven't had any problems since.