I want to see a combination VoIP/MVNO double-play. That’s one company that sells cellular service (using someone else’s network), sells VoIP service, and integrates the two services.

There are two specific scenarios that seem obvious:

1. They sell the customer mobile phone service and VoIP service via an ATA or SIP hardphone. This would be great for people who have turned off their home phone service while continuing to pay for some form of Internet access. One number would ring both devices, the first one to pick up wins. Outgoing calls would have the same caller ID from either device. Alternate products would be family plans with multiple phones, each with their own number, then a shared number that will ring all devices; and centrex plans for small businesses, where the company provides both VoIP desk phones and mobile phones.

2. They sell the customer mobile phone service and act like a SIP client. This way the customer can integrate their mobile phones directly into their existing phone system. Ideally, the MVNO’s SIP gateway will register and unregister with the SIP PBX as the phone gains and loses service; this will let the PBX do the Right Thing with voicemail, and also enable a number of other services.

Personally, I’d love to buy services like this. I’d prefer GSM phones, simply because the most interesting phones are almost always GSM-only. Accoring to Cellular News, there are at least three GSM MVNOs in the US right now, using both Cingular and T-Mobile’s networks, so this is certainly possible.

On the hardware front, several companies seem to be providing GSM/SIP gateway equipment:

• Bridgeport Networks seems to be marketing these exact ideas to carriers.

• Blueslice concentrates more on WiFi/GSM roaming, but the basic technology seems similar.

It’s possible that Earthlink will be rolling something like this out soon–they’re building a MVNO, and they share at least one board member with Bridgeport Networks. They seem to be concentrating more on EV-DO then anything GSM-related, though.

There seems to be a huge push in the cellular industry to integrate SIP into their networks, so something like this will be possible sooner or later. My current contract with Cingular is up in 6 months; it’d be nice if someone has something on the market that I can buy by then.