Motorola NewsCard Technical Info
The NewsCard will work with the IBM Simon, so the NMG might work there too. A Sun-Sentinel Article from 1993 says:
Other Newscards have been introduced that can be used with the Apple Newton personal communicator and with Casio or Tandy portable computers, which do not have built-in cellular telephones. (full article here)
This page indicates that it would work with the HP 100LX, too: “HP StarLink consists of an HP 100LX and the Motorola PCMCIA NewsCard..”