I know a decent number of folks in the Washington ski/climb/do-things-in-remote-areas scene who have em, though more common is the type that doesn't let you sms and doesn't have a monthly fee (basically a please help or I'm not getting home button). That said most of my friends with inreaches don't have the unlimited sms plan, and just budget the limited number for check-ins.
And yes, it's generally a good idea for anybody hiking in areas without cell phone reception - even if it's not particularly far out from populated areas! I live in North Bend, WA, and it feels like almost every year there's at least one hiker lost on one of the popular local trails. Sometimes they get lucky:
I mentally shudder every time I go hiking there, and see all the people dressed in cotton clothing and wearing street shoes (or even flip flops!) as they head towards the trail from the trailhead parking lot. Maybe there's something about well-maintained trails that promotes a false sense of security? Like, it looks neat and well-travelled, there's plenty of signage, so what could possibly go wrong? And it mostly doesn't - but when it does, it can get real bad real quick.
