|I tested it up on the moors on the way to the boat too.|
A what? It gives out a VHF signal on the 2m amateur radio band including its position and this is picked up by other stations and repeated until it (hopefully) gets to one connected to the internet. This means you can track it. In particular on APRS.fi which also tracks ships on AIS.
It is very good value at under £UK 78 on ebay. But it is a bit of a devil to configure. The documentation is in Chinese. But even if you read Chinese it is probably hard. Fortunately there is an Yahoo group (the unit is also sold as an AP510) that has the latest version of the software and other files (you need to update the firmware). There are also videos on YouTube to help.
The interface software that you need to set the parameters (like your ham call sign and the frequency) runs on Windows. It runs with the same amount of installation difficulty on Linux under Wine (mainly finding missing DLL and OCX files from Visual Basic which you have to put in various Windows System folders).
It comes with a little stumpy antenna. This will just about get your signal to the next room. So when you have figured out how to use it get a better antenna! The SMA connector is a little fiddly as the collar rotates when you screw in the connector.
Mine is currently on Tui at Humber Cruising Association. Here we are on APRS.fi. It is currently using a dipole antenna from Sotabeams made for plastic tubing bungeed to a stanchion.
You can even send one line emails over APRS - in this case using the app APRSdroid connected to the AVRT5 over Bluetooth. The GPS also stores position on a micro SD card. It has a rechargable battery built in , charged by USB. The battery certainly lasts a few hours but I have not tested that.