Here's a fitness gadget:
Notice the link at the top that says Body Fat Estimate? Clicking that takes you to the gadget creator's site.
Notice the other links at the bottom. They also go to that site, different pages than the first link.
Before I grabbed the code, Google let me specify the size and color for the gadget, which means site owners will be able to adjust the gadgets to fit them on their page.
Gadgets aren't limited to simple calculators:
Bet you weren't expecting that!