The first device is the inReach SE. It is a personal locator beacon for $300. This gear can send an SOS to a worldwide rescue service. The recipient can see the sender's GPS location with latitude and longitude coordinates. It competes with the SPOT locator beacon described in another equipment article on this web page. Some of the advantages of the SE are that it is a two way satellite communicator. The user can send and receive text messages with the rescue service, and other persons whose contact information has been pre-programmed into the device. The SE uses a world wide network of Iridium satellites. It also requires a service subscription for about $12 per month. The sender will receive an audio and visual confirmation of sent messages. It is water proof and has a rechargeable battery.
The second device is the inReach Explorer. It is essentially the SE on steroids for $380. It has all the same features, plus some mapping and navigation tools.
The third device is the Earchmate PN-60. It is a GPS with the biggest screen and the strongest mapping and navigation tools for $300. It can download from the DeLorme web site topographic maps of the entire USA and many foreign countries. But, the Earthmate does not have any SOS, locator beacon or text messaging features.
Conclusion: if you want to travel fast and light, the inReach Explorer has the locator and texting capabilities of the SE and some of the mapping features of the Earthmate. But the Explorer's mapping and navigation tools are not nearly as strong (and the screen is smaller) than the Earthmate. If you want to cover all your bases with the best combination of tools, then go with the SE and Earthmate, which is what is I carry.