GPS tracking devices

I know there are gadgets like the "SPOT" etc which are great (I assume).

Having just spent a big chunk of my super on a caravan, even though it's fully insured, I'd like to fit a small device that can serve 2 purposes:

1). It would be able to keep track of how many kilometers we've traveled... great for servicing intervals etc and for being able to be able to confidently say (around the camp fire etc) how many klicks we've done in the last 12 months etc. Sort of a modern version of the "Hubometer" that semi trailers use.

2). It would plug into an onboard power supply (eg: a USB port which is constantly alive) and would be able to be remotely accessed on my mobile phone (as an example). I'm assuming this device (which would be hidden inside the van) would need an external antenna similar to the type that an onboard GPS inside a 4x4 would use). The one I had on my last rig (Landcruiser) was mounted on top of the snorkel and was about 40mm x 40mm x 15mm. In the event that the van goes missing I would be able to log-on to an app on my phone and hopefully I would learn its whereabouts.

I know there are gizmos on the market that can do these tasks, but I have zero idea of what brands are reliable or where to look. I do a lot of shopping on ebay, but there seems to be a lot of junky stuff from China on there which I'd be suspect about.

Thanks in advance,

Bill Roach