Simple one-page website — input your cell phone number, select your phone carrier, and choose your own identity (email address) that will allow you to receive text messages to your cell.
As of right now, if I wanted to give you an email address that would send me a text message, it would be my actual phone number @vtext.com (Verizon). I think in the future we’re going to see a lot more mobile communications and users are going to want to hide their actual phone number.
The domain for this should be short (like ‘@mycell.com’ would be great — actually, I just looked and they appear to be doing somewhat I’m suggesting here as an idea). Additional options would allow the user to select whether they can receive images and/or videos to their cell phone. (This info would come in handy in the future.)
Then as the owner of the service, I’d expand with various offerings — sports scores to the user’s cell, alerts of comments to their MySpace page, groups created that allow users to blast messages off to their group for say an announcement of a happy hour or concert tonight, etc.
Also want to be clear that you will not spam the user.
What other free mobile services could this offer a user? Eventually you integrate ads to these users — particularly if you can send them sports scores, you could send them in that same message a one-liner ad from Pepsi or Coors (“Brought to you by Coors”).