Contact list

I've just set up sms framework + notification and it works great!
BTW I was wondering if it would be possible to send sms blast not just to a pool of users, but even to a pool of phone numbers!
The perfect solution I think it would be a sort of contact list created with a custom content type or just a list of subscribers as in every good newsletter.
What I need it's a way to keep in touch with my costumers without having to force them to register to my site.
TIA!