Recently picked up a GPSMAP 66i from Garmin. As many of you may know, Garmin purchased DeLorme (Makers of the InReach satellite communicators) a while back. This is Garmin's first GPS device with InReach functionality built in. It was a hard decision between this and the older Explorer+ model. Is the 66i really worth another $200??? For me, yes, I think so. As always, your mileage may vary.
If you are strictly looking for a communication device, the Explorer+ or even the Mini would do just fine. If you know me, though, I'm a gear whore and want all the features.The topo maps that come installed on the 66i are Garmin maps whereas the Explorer+ is still using DeLorme maps. The Garmin maps are better in my opinion.
The 66i also has a range of sensors built in as well as an ANT+ receiver for using additional external sensors. A 3 axis compass is part of the built in sensors and comparing it to my actual compass, it is reasonably accurate. It is lacking in the ability to sight objects though.
Additionally, it has an atmospheric pressure sensor. I have this page configured both to display my altitude as well as track barometric pressure trends. This is useful for predicting weather off grid. Though you can get satellite weather reports over the Iridium network as well.
I also have a Garmin Tempe temperature sensor and can read those data on my 66i as well.
And of course there's the satellite messaging functionality for which the name "InReach" is known. It's nice knowing that wherever I am in the world (full global coverage on the Iridium constellation of satellites unlike other products like SPOT which use the more limited GlobalStar constellation) I can send and receive SMS. Be it simple things like letting my wife know I'm not dead to requesting assistance.
And if the need is great, there's the SOS button on the side which will initiate a response through the GEOS monitoring service. Though this isn't a get out of jail free card. After pushing that button, help is still likely several hours away. But it's nice to have.
All in all this is a very powerful tool for off grid activities. I've spent the last couple weekends using it in the field and getting acquainted with all of its features and am very happy with the purchase.
Okay, ramble over.