You can read all about the device, and download the user's manual, from http://www.findmespot.com. The unit costs about $150, plus about $100/year for service, plus about $50/year for the "tracking" feature, plus about $8.00/year for insurance to cover the costs of private rescue services. I bought the whole package.
The tracking feature puts the unit in a mode where it automatically sends your position (lat/long) to a satellite every ten minutes. These tracks will appear in a "Google maps" format on a web page you can set up for the public to see, with or without a password. You also have your own home page at findmespot.com where you manage your account and the information you provide to the SPOT service in case of emergencies, and you can view the tracking messages there as well (limited to the last 30 days). The "shared" page you set up for others to use will only show tracking messages for the last 24 hours. This feature is in a beta test phase, and hopefully this limitation will be lifted when they release it for real.
People on this list and others who have followed my recent Alaska adventure may have seen that the shared tracking web page gave them a very good idea of where I was, almost in real-time (there appears to be a few minutes' delay before you can see a tracking message on the site, but I haven't measured it). The manual says the device will have a shorter battery life with the tracking feature turned on. I have used it for more than 60 hours now on the same pair of lithium AA batteries, with no sign of it losing strength. (Battery life will be significantly less in cold temperatures.)
As I gained confidence using tracking, I started to think of it as giving frequent position reports that SAR could use if I ever went missing on a flight plan and couldn't use the "911" button for some reason, like being unconscious or worse, or being down behind a mountain where the 911 call couldn't get out. Thinking about this, I came up with some ideas that might be useful to other SPOT users who fly off the beaten track. Here goes:
1. It took me several flights to work out the exact sequence of button-pushes on the SPOT device to make it do what I wanted. Here's what I did:
Preflight: 1) push the ON/OFF button briefly to turn the unit on. The light above it begins to blink. 2) hold down the "OK" button for about 5 seconds until the two lights above the ON/OFF and OK buttons begin to blink together. Now it's sending the tracking messages.
Post-flight: 1) press and hold the OK button until the light above it blinks red a few times (including a long blink). 2) when the OK light is done blinking red, press the OK button briefly. Both OK and ON/OFF buttons will start blinking together. Now it's sending an OK message. At this point you have to leave the unit out with a view of the sky (to the south, if you're in high northern latitudes) for 20 minutes to be sure the message is sent. I did this as part of my shutdown sequence, along with making sure my flight plan was closed. After 20 minutes or so, hold the ON/OFF button down until its light stops blinking, to turn off the device. Or if you're taking off again, just go directly to preflight step 2.
I recommend practicing this on a few local flights first, until you can consistently get the tracking and OK messages results you want.
SPOT setup: Before making the trip, I programmed the "911" Message Profile at http://www.findmespot.com with the following text, which is supposed to be read by the SPOT people who initiate a search for you:
"I am the pilot of N4401B, a maroon/white 4-place Cessna aircraft. One or possibly two souls on board. Please contact Flight Service at 1-800-992-7433 (USA) or 1-866-992-7433 (Canada). They will be looking for me if I'm overdue on a flight plan."
As part of every flight plan, Canada Flight Service will ask you for an emergency contact number to call if they can't locate you. (US FSS doesn't, but you can put it under "remarks" on the flight plan.) I chose my son, who knows his way around a computer and the web, and sent him a long email to explain what I wanted him to do if he got a call from FSS that I was missing. I gave him the password for my SPOT account, so he would be able to see tracking messages older than 24 hours. I told him he should make the tracking information available to FSS, especially the last position report, and if that happened to be an 'OK' message, they should look for the plane at what ever airport it came from.
I started telling FSS, when filing each flight plan, that I was carrying a SPOT Tracker that would be making periodic position reports to a satellite service (if I remembered to turn it on), and that my emergency contact would know how to access this information. The Canadian briefers I talked to all seemed to know what a SPOT Tracker was, but the US briefers did not (admittedly a small sample in both countries). I didn't start doing this until I'd left Alaska, so I don't know about the Alaska FSS people.
I'd like to find a simpler, more direct way to provide the tracking information to FSS. One idea I had is to register the domain http://www.n4401b.com, and set up a page there with information about myself, the airplane, emergency contact information, and a link to the shared tracking page with a description of how to interpret the information there. That URL would be pretty easy to put in flight plan remarks, and it might enable FSS to find me quicker than anything, without having to ask anybody. Assuming they can get on the web...

When you're cruising along behind your good-ol' O-300 over the wilderness, watching the ground speed and fuel consumption as you go, sometimes you start to think about things. I think I'd rather have this than an ELT, any day!
