Personal web-based live GPS tracker

I do most of my riding solo, not a smart plan, but that is how I roll. After a few recent tumbles and mis-adventures my wife has gotten to the point where she almost won't let me go out without supervision.
To rectify this I found an app for the Blackberry (or iPhone, Android, etc.) that transmits my GPS position to a website every X seconds (configurable). I then leave the website open for her to check on her leisure and it displays my position/speed/heading. She has instructions to try to call me or call the appropriate authorities should the fear of the worst arise.

I use this one, but I've read its functionality on the iPhone is limited (no background-ability though I'm sure there are many others for iPhone)
http://www.instamapper.com/phones.html

Just another handy tool that potentially may be there for you when you need it most.