The device, to have the model number 6315, is a version of the iPaq that aims to roam smoothly between wide area GSM networks and localised -- though much faster -- Wi-Fi hot spots.
The launch, due to take place today, according to a report in today's WSJ Europe, makes sense for T-Mobile. The Deutsche Telekom mobile arm has not only invested heavily in cellular networks in several countries but also in Wi-Fi, often through partnerships with companies such as Starbucks.
Even the data rates promised by 3G cellular technology fall short of connections on most Wi-Fi networks.
It is thought HP will offer the device in Europe and Asia, though it is not known which operators will become partners. Its launch price will be $499 (£271).