After reading all the posts here, it seems to me that participants in this discussion are seeking one of two different results:
The ability to leave a breadcrumb trail so that others can determine where you are, or;
The ability to send a distress message to others.
I think that there are much less expensive options available to fulfill either of the two objectives than dedicated systems such as SPOT and EPIRBs.
In my 'day job', I deliver new aircraft from the factory to the customer. The factory is on Vancouver Island in Canada, the customer is almost always on the other side of the world (Maldives, Seychelles, South America, Tahiti, Papua New Guinea, etc. - you get the idea). The aircraft are always equipped with an Emergency Locator Transmitter (ELT), which functions the same way that the EPIRBs do, so objective number 2 is looked after - if the aircraft crashes, the ELT activates automatically. But this functionality is reserved for only the most serious of emergencies - a crash, or perhaps a forced landing in a hostile environment.
This notwithstanding, all sorts of people I work with (my employer, the customer, friends along my route, etc.) want to be able to find out where I am at any time during my trip. It can sometimes take 10 days to get the aircraft to the other side of the world. I have quite deliberately dodged requests to "carry a SPOT", etc., simply because it would then become "one more thing" that I have to be concerned about - for example, making sure that the battery is charged, making sure that the thing has a view of the satellite constellation, and so forth.
On a recent moto tour through Eastern Europe (see Notes from a September 2011 ride through Romania, Bulgaria, Turkey, and Greece
), I used my motorcycle as a proxy for the aircraft, to enable me to try out different tracking solutions to satisfy goal 1) above. After a lot of experimenting, I came to the conclusion that Google Latitude
is the least expensive and least complicated way of leaving a breadcrumb trail behind.
It works like this: You set up a Google mail (gmail) account, then tie that account to the Google Latitude
functionality. Both are free. Once you have done that, whenever you log into the Latitude home page using a computer that has a Wi-Fi connection
to the internet, a breadcrumb is dropped from your log-in location. Anyone else that you authorize to view your location in Google Latitude will then be able to see where you are. For reasons unknown, connecting your computer to the internet via Ethernet (a cable connection) won't drop a breadcrumb - but connecting by Wi-Fi will.
You can increase the frequency of the breadcrumbs that are dropped by Google Latitude by installing the Latitude application on your mobile phone, and leaving the application running on your mobile phone. The application is available (free) for numerous different types of mobile phones, including Android, Blackberry, and others. If you leave the application running on your phone, and your phone has a GPS receiver and a view of the satellite constellation (fairly easy to facilitate, just leave the phone in your jacket pocket), then the phone will log into Google and drop a breadcrumb as long as it has both GPS reception and a connection to the local mobile phone system. I presume in this case that some data connection charges (from the mobile phone provider) will apply. I don't know how much data this application uses, I have not yet seen the bill from my September trip. In any case, you can easily limit the number of breadcrumbs dropped by simply exiting the Google Latitude application on your phone. If the application is not running, it won't pass any data.
All I really need to do to keep the people following me happy is drop a 'daily breadcrumb' so that they know where I am on any given day. I can do that easily enough by logging into the internet via a Wi-Fi connection once a day. That's not a burden on me because I do that anyway just to fetch my mail and read the news. You can use a public computer (doesn't have to be your own) - just visit the Google Latitude web-page and log into your account to drop the breadcrumb.
Below is an image showing how the Google Latitude application tracked me riding across Greece about a month ago. I had my phone (Blackberry 9780) in my jacket pocket, and I guess that the GPS satellite signals managed to permeate my riding jacket and get to the phone... so, the phone made a data connection to Google each time I went by a cell tower, and the result is what you see on the map. The breadcrumbs that get dropped are generally pretty accurate - within about 10 meters. Occasionally, one will be slightly in error (see the one in the middle of the water in the picture), but generally, they are pretty accurate.
The only 'disadvantage' to this system is that only you (the Google Latitude account holder) can see the historical map. Everyone else that you authorize to view your location (they can view it on a computer, or on their own mobile device) will only see your most recent location. I don't think that is a problem if the objective is number 1, above... Anyone who goes looking for you will see your most recent location.
As for making contact in an emergency (objective number 2, above) - provided you are in range of a mobile phone network, I think that just dialling someone on your mobile phone and saying "I'm in trouble, and this is where I am" is sufficient. If you have Latitude installed and running on your phone and you are in range of a mobile telephone network, then whomever you call can go to the Latitude website and see where it is that you are calling from, even if you don't know where it is.
I hope this provides some food for thought, and perhaps provides an inexpensive and simple solution for fellow travelers. A key point that must be kept in mind - and that I think might be underestimated by some participants in this discussion - is this: If it is not super-simple and super-easy for you to ensure that your "tracking device" is always broadcasting, then it's not a tracking device, it's just excess weight that you are carrying around.
Google Latitude Tracking History one afternoon (riding towards the Peloponnese)