We take for granted that we carry a phone with us all the time and can be reached anytime, anywhere. Sometimes calls or texts come through at inconvenient times or places, like in meetings or in the bathroom (!). If you need to ignore a call or text, you can use Clacsoft's AutoReply to answer via SMS to the party trying to reach you with a pre-selected automated response message.
All you have to do is set the rules for how AutoReply answers and it will take it from there. You can even set specific rules for certain numbers and a general rule to apply to all others. You can pick up AutoReply for your G1 Android phone right here.