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.
This is the personal learning edition of e-on software's flagship product, vue 6 infinite. If you ever wanted to play around with 3d environments and animations in an easy to use package, this is it. I have found vue 5 easel to be a wonderful program; this version blows that one out of the water. Granted the output is limited (watermarked) and it is only for non-commercial applications; still it is a great way to see if vue is what you are looking for before buying (and the easel addition is