There have been a number of articles announcing, including this one from Garrett Smith, on the impending release of the Linksys WRTU54G, specifically for T-Mobile's HotSpot @Home. It's a cross between an analog telephone adapter, router, and WiFi access point. And while it does transmit voice over an IP network, it's not happening in any most of us think of VoIP.

The HotSpot @Home service allows you to make calls over WiFi using a dual-mode handset. The technology T-Mobile is using is called Unlicensed Mobile Access, or UMA. UMA takes the protocol used by GSM handsets and encapsulates it into an IPsec VPN for transmission over the public Internet. The VPN is authenticated using the subscriber's SIM card via a protocol called EAP-SIM.

The upshot of all of this is that the call is encrypted between your handset and the provider's back end network. UMA also provides a way to fail between the native GSM network and WiFi. Since the same GSM protocol is used regardless of the transport used, failover between GSM and WiFi is certainly possible. T-Mobile touts it as a benefit.

The downside is that that leg of the call is the only one that has an IP component. The rest of the call terminates as a normal mobile phone call. In T-Mobile's case, you use the wireless minutes out of your plan and/or pay their normal international rates.

It's technically VoIP, but it's just a transport to their network. It's not VoIP as most of us know it. What do you think?