Here is some additional info for the T-Mobile G1 owners:
T-Mobile is rolling out a maintenance release (1.1 RC33) to G1 customers. In addition to Google Search by voice, the over-the-air update also includes Google Latitude, a new feature of Google Maps for mobile that lets you:
? See your friends' locations and status messages on a map or in a list. ? Share your location and status with friends and Google, while maintaining complete control over your privacy. ? Quickly communicate with friends through text message, IM or a phone call.