Air pressure gauge
I actually just bought my mom a digital one at walmart for $27.
Surprisingly, it has a generic, replaceable chuck and standard hose ends and fittings.
Most of the cheaper ones have "can't separate, or replace" hoses and/or chucks.
I only used it on her mower tires and truck tires but it's WAY easier for her to get them the same than those analog ones with tiny numbers and only 4 indicators between 10 pounds.