Any answering machine app (or widget) out there? Is there any app which can function as an answering machine, with multiple recorded messages, like "gone to take a shower", or "in a meeting" and easily switch between those?
Google Voice allows you to record different greetings and switch between them or assign them to different callers, unfortunately the app doesn't handle these things so you have to manage those settings on the web (voice.google.com). 

There's an app called Visual VoiceMail (not to be confused with your carriers visual voicemail app), that works with Phone Fusion's Fusion Voicemail Plus service which replaces your carrier's voicemail like Google Voice does and claims to allow you to change and schedule different voicemail greetings from their app.