Hydrogen peroxide powered rocket packs fly for around 30 seconds, because they have a specific impulse of around 125, meaning that one pound of propellant can make 125 pound-seconds of thrust, meaning that it takes about two pounds of propellant for every second you are in the air. Mass ratios are low for anything strapped to a human, so the exponential nature of the rocket equation can be safely ignored.

A pretty hot (both literally and figuratively) bipropellant rocket could manage about twice the specific impulse, and you could carry somewhat heavier tanks, but two minutes of flight on a rocket pack is probably about the upper limit with conventional propellants.

However, an actual jet pack that used atmospheric oxygen could have an Isp ten times higher, allowing theoretical flights of fifteen minutes or so. Here, it really is a matter of technical development, since jet engines have thrust to weight ratios too low to make it practical. There is movement on this technical front, but it will still take a while.

John Carmack

Won't the mp3-players be as useless as a betamax-player for the general public, as the copy-controlled cd's becomes more and more common?

sigh The copy protection that is being added to CD's is woefully inadequate to prevent it being ripped without serious backing from every CD drive maker on the planet (or alternatively every digital music player in the world...).
The existing set of CD players have to be able to recognise the bitstream on the CD as music (i.e. sufficiently close to the redbook that they will output a decent enough audio signal). Therefore a sufficiently intelligent combination of hardware/software will also be able to do the same.
And it doesn't even have to be that intelligent...They just have to recognise bad/conflicting data and assume/be told that it is to be interpreted as cd audio with the necessary interpolations over bad data.
Copy protection requiring hardware agreement in a non closed (i.e. no paladim) world is unlikely to work - see the sites showing you how to hack out the copy protection on minidisk..the reason this is not a terriby big deal on mini disk is that the transfer medium is a physical so passsing around dupliates is expensive and time consuming compared to kazaa/ gnutella / lan parties / warez medium of choice.
CD copy protection has a very short life span in my book because there is very little likelyhood that the DMCA could realisticly be applied to hardware/software that corrects 'damage' because that is all that can be done in the existing framework - damage the data.
Now if they comeup with a solution that replaces CD's with DRM built in it's a different proposition - still breakable perhaps depending on the algorithms and implementation (and of course on the legal system backing it up). But there's no way to bolt on DRM to something like CD's, and things like DVDA don't seem to provide much more to be honest. Your mp3 player will have a lifespan longer than its avaerage lifespan methinks.