The civilian sat phones I have used aren't much more rugged than an older model cell phone. However if you keep it in say a Pelicase and don't use it till you need it then it should be as good as a plb.
You will also need a GPS so you can tell help where you are - I don't know how good the location fix for a sat phone is but I suspect it is very poor - 100s of sq. miles if just based on which sat picked up the call.