Volume? Silent Mode? Vibrate? I don't think I've used the volume buttons on an Android phone for over a year.
You guys should consider using Tasker. You can react to anything the phone can sense or know about (e.g. location, running a specific app, time, coming in range of given WiFi SSID or MAC, plugging in USB, plugging in AC power, orientation, etc etc... you get the idea, hundreds of options), and then change absolutely any setting or settings on the phone, send specific SMS messages, do HTTP POSTS... I mean this is one hell of a powerful and really cool app.
Some examples what I do with it:
If I lose my phone I can text it a special code and it'll text me back its location with a nice shortened google maps link, and full details of any WiFis in range.
If it's after 11pm, and I plug in an AC adaptor to charge it, and it's face down, it goes into silent mode (because I want to sleep). It'll automatically come out of this when I unplug the charger.
It can do everything that Locale does (e.g. settings silent mode etc when you approach the cinema), but it doesn't send personal information to third-party servers without your knowledge. It works with Locale plugins too.
Whenever I use any app that really does need GPS for precise locations (e.g. Google Navigation) I have it turn the GPS on, and back off when those apps exit. I don't like random apps knowing my location.
When I leave range of my home WiFi, I have it turn the brightness (if it's daytime) and volume up, as I'm likely to be outside.
Anyway - it's some cool stuff is that app. It's utterly awesome, and nothing remotely like it can or will ever exist for the iPhone due to it's pseudo-multi-tasking.
Check out the "usage examples" section of their homepage: http://tasker.dinglisch.net/