Auto Text Message - Android App
It's called Auto Text message.
I wanted a way for my wife to send me a "I'm on my way" text every day when she left work to pick me up so we could carpool home.
In future updates I'm going to work on a shortcut or widget for the contact.
I might also change it to allow 2 or 3 preset messages with contacts.
See the App here
I use this with my HTC Evo 4G that I love.