So the moral of the story is: Check your tyre pressure's on a regular basis!
I too have invested in a digital tyre compressor from Halfrauds!
Yeah I bought one from them over a year ago. What peeved me off about it is how accurate you have to position it, otherwise you just let air out the tyres!
Also, I check before any motorway mileage is to be done, otherwise every two weeks (it got a bit much trying to do it every week).
Never, ever use the guage on "tyre inflator pumps", even those with digital presets. Just use them to pump up the tyres, and then double check with a separate tyre pressure guage - either on of the PCL pencil types, or an analogue dial type. Digital pressure guages should be avoided at all costs - they are unreliable, can not be calibrated at all, and give false readings if the battery gets low (but you would not no the battery was getting low - until it was too low to even power up).
Sometimes, old skool is still the most reliable!