been backpacking with one for a year. not for tracking, but emergencies since i backpack with my 5 and 7 year old. we do test it now and again while in the field and all the folks we have it set to send messages to get them, but at different times in the same day. not sure why that it, but it could be based on their own email servers. i hope/assume the emeregnecy call button gets a quicker message through to the authorities.

not perfect, but a bit of added safety