Start voice calls via Twitter? No way! Way.

Would you like to talk to your Twitter friends or set up a spontaneous conference call? Normally you’d have to agree to hook up over Skype or something else. But soon you could be making calls via Twitter.

Phweet is a new piggy-back Twitter service which does just this (thanks to Pat Phelan of MaxRoam and Twitterfone for the tip-off). After signing in with your Twitter name and password you select how the call will be carried, either via browser, SIP ID or number/Mobile Phone. You then plug in the Twitter username of the person you want to call. The system generates a “Phweet” which is a unique shortURL. The “PhweetUrl” calls you and you can share who you are talking to without having to reveal or exchange phone numbers or other identities. Once the conversation ends, the unique URL expires and the session message board disappears.

This is impressive. Connecting Twitter, web calls and conferences to the PSTN is no means feat. And because it uses open SIP services, it will work on many new Nokia phones with WiFi, as well as connecting to PSTNs. The whole thing appears to be free. Phweet plans to add more social networks and the Phweet API is going to encourage application developers to come up with new apps.

The founders are Stuart Henshall and David Beckemeyer, architects of TelEvolution which created the PhoneGnome VoIP service.

I doubt many phone networks are worried by this development, but it does show just how powerful Twitter’s service could potentially become, as a backbone for services like Phweet.