Tasker

Ok, I have to rave about my favorite thing for Android -- Tasker. If you own an Android phone, and you enjoy the process of fiddling about to make it more and more useful, then Tasker is the best thing ever.  It's an app that lets you basically attach various actions (changing settings, playing notifications, launching apps, etc) to various triggers (locations, times of days, phone sensors, phone calls/texts -- just about anything you can think of) in all sorts of interesting and complicated ways.  It's relatively expensive for an Android app (around $6), but worth every penny.

The only problem is the user interface -- it has a goofy unintuitive UI that makes it pretty cumbersome setting up complex profiles. I'd pay another $6 for a decent editor on my actual computer. (It's tempting to write one, as tasker saves and loads its profile scripts as xml).

That all being said, here's the things that I currently use it for:

• When headphones (without a microphone) are inserted, and there's no media already playing, immediately launch my last music player and resume the last song.
• Mute the phone on sunday during church time, and restore the volume afterwards.
• Mute the phone if it's being charged after 10pm. (I always charge it while sleeping, so I figure if I'm up after 10, I want it to ring until I put it on the charger. And if I'm charging during the day, I want to hear it).
• It checks my work calendar, and automatically mutes if it's during the time that I have a meeting scheduled (and restores the volume afterward)
• If Sara's calling, it vibrates with a crazy different pattern, to make it more obvious that it's her.
• If I get a call that's a non-217 area code, and not in my contact list, it's a different ringtone (I've gotten a lot of phone spam recently, so this makes it obvious it might be spam)
• If I get a call from a number I've previously marked as spam, it doesn't even ring.
• If I text a secret code to my phone (or Sara's), it turns to full volume, and rings like crazy (to help find the phone if we've misplaced it, or if I know Sara muted her phone and I need to get her attention)
• If I receive a text message, and I'm in the car (based on being connected to the bluetooth device in my car), it reads the text aloud over the audio.
• If I get a text message, and I'm not at my desk at work, it forwards the text on to my pebble watch. (If I'm at my desk, I get the text notification on my computer, so I don't want it to bother with my watch).  To check whether I'm at my desk, it does a web query to a URL I set up on my work machine that simply reports the time since the last input. If that number is bigger than a few minutes, it assumes I'm not at my desk.
• I haven't finished setting this up, but I want to do the same thing with gmail -- if I'm not at my desk, forward the message summary (First few lines) on to my pebble watch.

That's just a tiny sample of what this thing can do.  There's a thread here on Reddit with people listing cool things they've made it do, and some other interesting samples on Tasker's site. Like I said, if you have an Android phone and you enjoy futzing around to automate your life, Tasker is absolutely worth it.