I setup Google Latitude on my Blackberry. Google Latitude is Google Maps but allows you to view approximately where your friends are at. For instance, my sister also setup Google Latitude and I can view approximately where she is at using Google Maps. The downside of the service is that the Google Maps isn't always updated that often. For instance, my Google Maps just updated but before that, Google Maps did not update her location for 39 minutes.
The other downside of Latitude is you can not view your history. For instance, last week I went rollerblading around 25km but I wanted to see my path on Google Maps however I couldn't since Google Maps does not have the ability to show where you have been but only where you are.
While some may cringe at the fact that my where-abouts are available to anyone I have on my Google friends list, I am not so worried as the only people who will have access to see where I am currently is the people who I am close with or friends visiting the city who may need help getting around.
Don't forget to subscribe to John's blog via email. This will notify you of all blog posts on web design, web development, social media and the odd post about PEI. Just enter your email address in the box to the left.