Huh? Big magnet? From what I understand, an ECM (engine control module, the ECU or brain) has the map information actually physically burned into a ROM chip that can't simply be wiped out by a strong magnet. Actually from what I've read, the whole magnet/computer problem is typically pretty overrated. A powerful rare earth or electromagnet might be strong enough to screw with a relatively unprotected and exposed floppy disk, but poses very little threat to an actual computer or computer hard drive. Hell, the speakers sitting next to your computer on your desk and even the small one actually physically inside your case have magnets.

An ECM can increase your rev limit by raising the rev limiter built into the ECM. All engines/cams can only rev to a certain limit and still make power. Look at any dyno plot and you'll see the hp peak and drop after a cretain point, typically 300-500 rpm before redline. Increasing engine speed beyond that point has zero benefit because your making less power than you are before (remember at 8000 rpm your intake valve opens and closes ~67 times a second, only so much air and fuel can get in there in that amount of time). Also, you valvetrain isn't designed to rev much beyond that point and if forced to, can't keep up and it's possible for a valve spring to not have enough strength to push a valve closed when the cam lobe leaves (remember, 67 times a second) and leave the valve in the middle of the combustion chamber when the piston comes up and make contact. This result in bent valves, damaged pistons and a blown engine.

I don't know much about H22A automatics but I can tell you that mix and matching them isn't going to be easy or maybe even possible. To control a '97+ Prelude tranny, you'll probably need a '97+ Prelude ECM. That ECM won't work in your '95 Accord because your car is OBD I and the ECU is OBD II (different plugs and your car is missing sensors the later OBD II ECM will need to see). Automatics aren't really worse than manual trannies but have some disadvantages. They absorb more power than a manual and generate a lot more heat. They also may not be able to rev as high (maybe the reason for the lower redline on an automatic H22A).

I would say your best bet to increase your cars output would to be to go with a standalone engine managment system to control the engine itself. The only problem is I don't know what you would have to do to keep the transmission happy. If you build the engine to rev to 8000 rpm and the tranny shifts at 7100, it's basically pointless. Like I said, I'm not real familiar with H22A issues but I don't see any real easy solution to your problem.