The Power FC is a full ECU replacement. That means that you will be taking out the computer in your car and putting in the Power FC in its place. The new ECU(Power FC) has loaded into it basic Celica Driving maps, and also custom maps can be made using the Power FC Commander Unit or you can take it into a shop that to have it dinoed and tuned(the most efficient way to tune and will get better results)
The Power FC itself can be used as a replacement for most other cars, however, for each new car you will need to buy new harnesses and software. Now you could buy a Apexi Power FC Commander unit and software, and charge people that have a Power FC in their car money to tune their units, but their wouldnt be much buisness in it because you dont have a dyno and the tuning wouldnt be optimal.