Earlier I proposed having the laptop software provide required braking distance from V1 and using that as a signpost, but Oakape ably pointed that a bad weight invalidates the braking distance.
An alternative is having the software show time to 80 kt.
Assuming the software integrates thrust, acceleration and speed over time (as opposed to simply looking up static tables), time and distance to V1 are numbers the software must derive for a particular runway, weight, altitude, temperature, gradient, thrust setting, wind component etc. since the required runway length is the sum of distance to V1 plus the greater of braking distance for a V1 reject or distance to screen height without an engine plus required margins. On the way to V1, the software also derives the time and distance to 80 kt.
If you don't have 80 kt. by the expected time, you are either over stated weight, under thrust, have a brake dragging etc.