A friend recently asked me what strategy I used in Jetpack Joyride to crack the global top 10 (I've since slipped to 60-somethingth place or so). Figured I'd cc: the tips here on my blog in case they can help any other players boost their distances.
You can only use a single revive and a single bomb from your stock on each run. So you have to rely on also catching a revive on the final spin and a few score-nudging blasts. Obviously when you get out to 6K or 7K metres, you stockpile quite a few spin tokens. I think in my 10.8K high score run, I bagged 14 spin tokens total. If you're going for high scores and don't have both a revive and a big blast in your arsenal, you're doing it wrong.
The rest is all about maximising the distance you get each time you pick up a vehicle and then surviving long enough to get to that next precious vehicle pick-up. I've gotten adept enough with the vehicles to average close to 800m or so before colliding with a zapper or missile.
As far as screen position, you have to use short taps to keep a middle cruising altitude. It's the only way you can react quickly enough to the zappers. Also, when you ride the floor or ceiling, you have a tendency to do really wide swoops, which are hard to stabilise in time to deal with upcoming obstacles.
I'm playing on iPhone, which puts me at a slight disadvantage in terms of obscuring approaching obstacles with my finger. The solution I settled on is cradling the phone in my left hand and tapping the screen on the bottom middle with my right index finger. I find that my index finger allows me more tapping precision than settling for thumb mashes, which are inevitably slower and clumsier.
I use the rainbow jetpack but not for any mechanical advantage. (As far as I can tell, the mechanical differences between the jetpacks are imagined. As the progression speed ramps up, the game scales Barry's reaction speed accordingly so the physics morph in tandem.) I use the rainbow jetpack precisely because it doesn't kill any scientists on the ground below. It's too tempting to watch their funny bumbling death animation, which can pull your eyes away from the onrushing zappers.
Hope this helps. Good luck!