This week, Sprint (NYSE: S) and Motorola (NYSE:MOT) released two phones designed to work on both the Sprint and Nextel wireless networks.

While WiFi-cellular dual-mode phones are nothing new – T-Mobile (NYSE: DT) has been trialing their HotSpot@Home service in Washington state since October – cellular-cellular dual-mode phones are something of an anomaly.

In this case, Sprint is trying to wean its Nextel customers off Nextel’s iDEN walkie-talkie network onto Sprint’s CDMA network, which will soon sport high performance push-to-talk.

The market wants VOIP over mixed-mode wireless. In Nemertes’ benchmark, “Building a Successful Virtual Workplace,” nearly 76% of IT executives developing mobility strategies are interested in dual-mode phones, hoping they’ll reduce costs, and are even willing to pay more for phones if service costs go down.

.......