- Group messaging, need to create an account first (doesn't require personal information or confirmation). It is US Cellular but works for several other providers I have used it for in the past: http://usc.ztango.com/usc_wm_login.html
- May also be of use: http://www.google.com/tools/firefox/sendtophone/faq.html
- And the reference to AIM Invader sounds like some lame kiddie tool like the AOL Chat Room stuff from back in the day if any remembers those Punters. Didn't know they still made crap like that.
Most IM services do allow you to send SMSs to clients if available and allow them to setup receiving all text message to cell phone. I believe I have set up Yahoo and AIM to do this in the past.
- Posting Items from and to various other services: http://en.wikipedia.org/wiki/SMS_gateways
- Software: http://www.stumbleinside.com/
Yeah, I didn't send the time to make it look purdy, but the nfo is there.