I have been using "Spot" for over a year now. I don't leave tracks, I just send my wife "I'm ok"
or "running late" messages. It has always been accurate with my location and got the message out every time, if used correctly.... I have the $99 a year basic plan.
The Spot is on sale for $99 at London Drugs right now, I'm not sure if that includes the $50 rebate that is offered from Spot, till Dec 31 2012. So about $150-$200 for the first year and $99 a year after that.
I would like to buy the "Inreach" in the future, for it's ability to receive messages from home and for the comfort of knowing my message or SOS is received. They have plans starting at $15 a month and you can suspend your plan in the off season. $229 at London Drugs.