Spok / USA Mobility
Spok (formerly known as USA Mobility) offers the largest 2-way network for the legacy Motorola T900 and the newer Unication M90 two-way pagers. 2-way pagers work mainly in major cities across the United States and allow you to email back and forth between each 2-way pager as well as any device that has an email address. Add the SMS text messaging option and then you can also text cell phones. They do not rely on cellular transmitters and do not have GPS tracking.