No I think many people will want it. It is practical. How many times did you had to go to the ATM before going to the pump? or filled only 10 or 20 riyals because you did not have enough cash in your pocket, or the wife or the kids have borrowed some money in the morning? How about around the end of the month? It can be practical. I am not certain it is 350 QAR practical. SO I will probably install it once it is free or at least cheaper.
However there is a major question that needs to be answered. What happened once you sell the car? Can the postpaid be changed to a prepaid? can you just cancel the account? What about any prepaid cash in the account? What if the new owner does not want this in his car? can it be removed?