Take-off performance charts are very sophisticated taking into account all factors affecting take-off performance- aircraft weight, aircraft flap configuration, surface wind,air pressure, temperature, runway contamination, runway length and slope, local terrain, noise considerations. You can calculate minimal power to get airborne (for prolonging engine life) leading up to a 25% reduction of power. So, set the power, take-off at the right place, and it all falls into place! The calculations are good.
So these fancy 'acceleration detectors' are sounding perfect. They are useless. For a start, in varying wind on the take-off run, the airspeed leaps ahead or falls. If you are using an inertial system that only measures groundspeed, then again, it is affected by wind effects. A very large headwind component will lead to an early and very short take-off run with low acceleration.
I would suggest a crew that messes up a take-off calculation will be so hopeless that using an automatic acceleration 'meter' will be beyond their capability! The accepted wisdom these days is that rejects at high speed are more dangerous than getting airborne! The system works fine. In fact, BA uses communication with the main computer to calculate the take-off data for the pilot, so human error is removed from the system.