You can also use it to inspect your rain gutters! I was really paranoid about drones in the 70s-80s, but I had time to get over it before they really showed up.
I got to buzz myself with the Parrot with its iPad controller last week.
This doesn't give you a top speed; but I'd estimate 40-60mph based on the Doppler shift and imagining having to chase it with a car:
ryannoe -- This video used a GoPro Hero 2:
mwc quad // floating on Vimeo