Yes, there are fitness trackers for dogs too. FitBark ($69) uses a 3-axis accelerometer that includes a waterproof case that attaches to your dogs collar. It monitors steps, sleep and behavior with the goal of improving your dogs health. There is an App compatible with iOS and Android devices.
One of the more interesting aspects of this product is how FitBark is mining the data to understand canine activity. Seriously, check out the data mining link if you are into dogs. The graphs are findings are fun. Did you know that Golden Retreivers like to spend 65% of the day resting? It might surprise you that Massachusetts has the highest dog activity followed by New York and Colorado. Check out this Daily rest by Breed, Weight & Age Range.
For the canine fitness hackers among us there is a REST based FitBark API. Here is an example to see what a request and response would look like for a three days of activity in June.
GET ACTIVITY TOTALS
Get historical activity data by totaling the historical series between two specified date times.