I've been using a SPOT Messenger for a number of years on the PNW and Inside Passage and I can't imagine being w/o it now. It's especially helpful where there is no cell phone coverage because it allows you to deviate from your float plan and let family/friends know where you are and that the deviation/delay is intentional and that all is well. Cruising is much more enjoyable when you're able to linger in a nice anchorage, spend some time fishing, or explore a new location w/o worrying about worrying those that expect you to be someplace you're not. It eliminates the pressure to reach a destination before someone reports you as overdue.
It also enables you to request non-emergent assistance from family/friends or emergent distress assistance (Coast Guard) via the SPOT dispatcher.
The new SPOT Connect (which I don't have) also allows you to send text messages via a smart phone.
I've never had a problem with coverage or reliability of the system. I don't leave the harbor without it. The subscription fee (~$12.50/month) is cheap peace of mind.
Norm
'76 CHB 34' DC
Poulsbo, WA