a heavy 747 take-off doesn't compare to a light 737 or Q400 take-off
Rainboe is absolutely right. I like the logic of a device that tells me the acceleration is normal, but I just can't see it working in practice. There are just so many variables - particularly wind - that it would be fooled far more often than it got it right. As for something else to monitor during the take off roll - here's the problem. Our SOPs on the Q400 are for PF to advance the power levers slightly and call 'set power'. PNF advances them (slowly) into the detents, calls 'power set', 80kts both, V1 etc. At light weights it all happens so quickly that by the time power is set, you're practically at 80kts, and V1 comes up within a few seconds. There's barely time to monitor the engine instruments, never mind anything else. It goes like a bat out of hell, even with reduced take off power.
Compare the number of incidents caused by abnormally slow acceleration with the number of aircraft that successfully get airborne each day, and you have to say that the system works very well as it is.