The XDA (Converged Digital Assistant), which is due to be launched in Europe next year, will be based on Microsoft's recently released Pocket PC 2002 platform.
It will have a permanent connection to the Internet via mm02's GPRS (General Packet Radio Services) networks.
Pocket PC 2002 features improved wireless connectivity and the ability to retrieve e-mail through a company's security firewall. Analysts have predicted that the specification will boost corporate uptake of mobile devices.
The XDA is capable of unified messaging, which allows users to receive voice mail, e-mail, text messages and to make and receive calls while browsing the Web without having to keep reconnecting to the Internet.
John Davies, XDA marketing manager at mm02, said the company sees the device as "defining a new category for mobile devices".
Unlike devices such as Nokia's 9210 Communicator, which is based on GSM, the XDA is based on the faster GPRS network. "The main thing is that it offers full integration. It is not simply a phone latched on to a PDA," said Davies.
Suppliers have been watching integrated device developments for some months, although few have come to fruition. Mobile phone operators Nokia and Motorola recently scrapped plans to develop integrated devices with handheld company Palm.
Motorola also pulled out of a smartphone venture with UK handheld maker Psion to build devices based on Symbian's Epoc operating system. Microsoft still plans to release an operating system, codenamed Stinger, for mobile phones which will compete with Symbian.