Google Voice for Android is the mobile phone interface to a free service that is still in a beta testing phase. Google Voice attempts to merge voice telephony into Google's virtually instantaneous information delivery system, but it does so with sometimes unintentionally hilarious results.
If you have a Google Voice account, you're able to make voice phone calls from a computer anywhere using the phone number assigned to the Voice account. With the Android app in place, you can use Google Voice to make phone calls or send SMS messages using the Google Voice phone number you chose when you signed up for the service. If you set up the service correctly, it automatically routes voice calls and texts sent to your Google Voice phone number to your Android handset. Domestic calls or texts made using a Google Voice number are free; international calls cost money.
Google Voice has a number of nifty features that your typical phone service doesn't. For instance, if you receive a call to your Google Voice number on your handset, you can decide to send the call to voicemail--then listen to the message as it is being recorded in near real-time. When the caller is done, the service sends a transcript containing the text of the voicemail message and an audio file to the Google Voice app; if you didn't listen to the message in real time, you can listen to it after the fact, or just read the transcript.
These transcribed voicemail messages are where the unintentional hilarity comes into play. More often than not, the machine-transcribed messages don't quite match up with what people say. But you can always play back the audio recording of the message, which (as it plays) highlights the word the speaker on the message is saying.
Messages saved on the Android phone don't survive a factory reset, but they remain available on the Web-based service. It's too bad the messages don't automatically synchronize with Android after a reset, but it's a small price to pay for free U.S. telephone calls.