Didn't someone suggest an app for the 500 manual and when ridiculed (a little bit) the point was made that the manual was at home and he/she was 300 miles away with a blown fuse or something.
Surely the same could be said for having the bulb app, as you never know when you might have to replace one when miles away from home.
Of course if you have the 500 handbook app then it will tell you the type of bulb, the type of oil, the tyre pressures, where to jack up the car etc. etc.
Yeeeees BUT, If a bulb is blown then you have the blown bulb as a reference. Hmmmm my headlamp is blown, get it out and see what it says on it
With a blown fuse it's far better to know exactly which fuse does the job and also the amperage as someone may have put a 10 amp fuse where there should be a 5 amp fuse.
When the W5W bulb for the numberplate blew, I simply took the old bulb out and bought an identical bulb to replace it......
I bet I'm the only person on the forum who has every sort of bulb (other than the DRL ones) spare and in the car