The MobileModem sled will allow users of PalmV/Vx and IBM WorkPad c3 PC Companion handheld devices to connect to Motient's wireless network across the US and Canada.
The MobileModem sled fits onto the back of a device and costs $179 (£125) on Motient's Web site if users sign up for a 12-month contract to the company's wireless access service. The service starts at close to $40 per month and the sled is scheduled to ship in the US in early December
The sled only allows users to connect to Motient's network, said Walt Purnell, Motient's chief executive officer, at the Comdex trade show. The MobileModem, which weighs about 4.8oz, will provide users with always-on wireless access.
The company will release a similar sled product for Compaq's iPaq device in the first half of next year, Purnell said.
Motient resells the BlackBerry two-way pager from Research in Motion (RIM) and provides wireless access for it. The company also customises wireless service for large organisations such as UPS, adding applications or adjusting hardware.
With an always-on connection, the MobileModem will "wake up" a Palm when it receives an incoming message. The product supports Microsoft's Exchange, IBM's Lotus Notes and Novell's Groupwise messaging systems.
The extra weight may not appeal to some users, but Purnell was confident that the large existing user base from the Palm and IBM devices would provide enough potential customers.
While business users make up the majority of Motient's customers, the company is working on developing a more consumer-friendly wireless service that would include a lower monthly subscription.
Lower monthly subscriptions could be offered to users whose devices are capable of instant messaging but cannot download e-mail messages, because they would not consume as much network bandwidth, he said.
"Kids don't need to access their corporate e-mail accounts, and I know that IM will not drive the same kind of network traffic," Purnell said.