With a Wi-Fi phone, they could make Internet calls from home without the need to run wires to the broadband line. Customers could use the phone number of their existing Vonage service or a new one for no extra fee.
Authentication, or providing credentials that let you use a given hotspot network–whether a paid login or a WPA encryption key or handling 802.1X, even–is the biggest stopping block in allowing VoIP over hotspot to work. A technology like EAP-SIM, which would use a GSM SIM module to authenticate, might be one method of logging in. But it requires every hotspot or hotspot network that wants to allow this sort of connection to build the back-end to handle it.
Various reports suggest it should be available this Spring or early Summer for around $100.
Seperately, but related, Engadget reported VTech is taking this issue from the other side and has released a Wireless-but-not-WiFi VoIP phone. “It’s a cordless phone that comes with […] a VoIP gateway chipset built right into its base station, which you just connect right up to your router.” Since most WiFi VoIP phones will be essentially fixed base products for the short term, this sounds like a somewhat less complicated solution for the interim. The VTech site isn’t updated yet, but there’s a picture in the Engadget story.
[update:] The Engadget crew got their hands on one of these during CES. More pictures and details there.