It's Go800 (go800corp.com), and it allows people to call your phone by texting your Twitter name to 46800 ("go800" on phone keypads). You can connect your Go800 enabled name to just about any sort of phone number, including mobile, landline, Skype, toll-free or Google Voice numbers.
The default is for your Go800 name to be public, meaning anyone who knows your Twitter name can call you. A feature that allows you to block unwanted caller's numbers is in development. In the meantime, David suggests attaching Go800 to a Google Voice number as GV does offer the ability to blacklist unwanted callers. You can also set go800 to "Friends only" which limits you to receiving calls only from numbers you specify.
What's novel and disruptive about Go800 is the idea of connecting people with names rather than numbers.
I can see a lot of uses for this. It seems especially suited to brands, activists and businesses who want to make it easier for prospects and customers to reach them. Giving people the ability to contact you using a memorable name (like your brand name) instead of a bunch of numbers strikes me as a great way to encourage call backs and drive sales.
For individuals, Go800 provides a way to let people you meet call you without revealing your phone number to them. Plus people are more likely to remember your name than a number.
The service is currently limited to US and Canadian numbers. Go800 plans to support users in other countries soon. Even if you aren't in the US or Canada, you can sign up now to reserve your Twitter name as a Go800 name. After 90 days, Go800 will start letting new users register any word, which obviously could include registering someone else's Twitter name. So it might be a good idea to register your Twitter handle soon before someone else grabs it.
Go800 uses a switch rather than VOIP to connect your number with the Go800 user's phone. That means that calls are charged as normal phone calls, including any surcharge your operator levies on calls between the US and Canada. When Go800 launches international service it will use VOIP and calling rates will be competitive with other services like Google Voice and Skype Out.
The first 100 minutes of calls per month are free. Currently there isn't any way to buy additional minutes. Go800 is working on letting users upgrade their account to handle more calls.
David says that Go800 will soon offer the option to use a mobile Web app instead of SMS to initiate a call.
Go800 costs nothing to get started, no credit card is required, just a Twitter account, phone number and email address.
Visit go800corp.com to Go800 enable your Twitter name.