Gear Ratio Detection for Custom Ratios

Hi! I was wondering if could be usefull to add a button per gear for calculate while car is moving instead only have the option to put a real gear ratio, you know all brands have 3-4 gearbox that could fit to the same engine and not always we have the real gear ratios on hand even some of these are difficult to find these. I was wondering if could be added something like this , i think will be very helpful for easier gear ratio calculation on the fly. Also the way to find pulses per ratio using GPS would be helpfull, i always think simple things are better if will works really good. here an example , this is used from other plataform, Im not saying to copy but the fact that simple way to get it working is very helpfull for any FOME user. Thank you!!