I have that ability when using my Laptop with my mapping software through Co Pilot live. For anyone wanting to track me, I must have my wireless connection going on the laptop, and I must allow them access. It really is a nice feature, as when headfing for a destination in the Motorhome, people I am going to visit can see were we are and what kind of progress we are making. It also allows receipt of instant messages from people with access, and they pop up on the screen...
I don't know about the tomtom access. But, as they have a way to track buddies, if you have a live wireless connection... I would guess it would be possible... I don't use my tomtom one xl with that function in mind, so I can't help you on that specific.
Tom