I have one in each car. One is a plug in compressor with a digital gauge and pressure setting to shut off the pump when that is reached. Has a torch as well built in.
The other came with my Suaoki jump starter pack - runs off the jump pack with a simple dial pressure gauge. Not used very much but sits neatly in the case with the rest of the pack...like this:
I only really use them if I need to check the tyres and the fuel station is closed or to top up my spare winter tyres if/when I put them on.
I will say they are handy if you have a car that is mothballed / stored and when you need to move it the tyres need some air...but they take a fair while to move the volume of air needed for a flat!