The Jetpack: From Comics to a Liftoff in the Yard
OSHKOSH, Wis. — To rise off the ground wearing a jetpack is to feel the force of dreams. Very, very noisy dreams.
John Schwartz of The New York Times tested a jetpack with its inventor, Glenn Martin, left, and Ray Thomsen guiding him. The device was unveiled Tuesday at an air show in Wisconsin.
http://www.nytimes.com/2008/07/29/science/29jetpack.html
The only issue being that no jets are used, so the word 'jetpack' is a misnomer.
But still it is a working jetpack (propellerpack) and if he could get the system to work for longer periods of time it could be sold for a lot of money. 
On MythBusters, they put together a similar "Jetpack" from plans off the internet, that used an engine with less than 100 hp, had a gross weight of about 300 lbs, and couldn't get the thing off the ground. The Martin jetpack uses an engine rated at 200hp, has a gross weight of 535 lbs, and delivers 600 lbs of thrust, or 3 lbs/hp. If the MythBusters configuration was as efficient as the Martin, they still couldn't have flown, they were just underpowered.