I have the inreach explorer and really like it. I have the earthmate app on my I phone. I put the I phone on airplane mode and enable the blue tooth. Using the app you can text like a regular cell phone via the app so it will only take texts with people you are in conversation with on the devise. I sent bbtoys a text from sprit lake in Renshaw and he responded back in less than 30 seconds. We were talking back and forth testing this. Then when we were heading back to the truck we sent a text to bounce that we were in a certain area and he can meet us at the staging area, they responded and asked me if I could do something for the groomer. A guy had a broken A arm. We texted our local buddy and one was puts aside at the local shop. The navigation works great as well. I really don't see the point of any second devices as this has many features. While playing around with it I went in to the max plan to see what I would average use. I figure the plan to get would be the discover for 29.95 month. Rubbing this from 8:30 am till 6:00 pm the battery runs down to 84% in a day with moderate use. It has a battery charge indicator that counts down and tells you battery condition.
My only suggestion would be to install a power adapter (cig lighter) on your sled and carry the car charger for it. I know a couple of people that have pulled their inreach out to find they had left it on and battery was dead.