What to use?

Eddy I dont have one of those but would like to get one just as a secondary backup. But I just do it the old fashioned way. I keep a logbook with my compressor. Stating the running time, size of tank being filled and from starting pressure to finishing pressure and the ending temperature. Also oil changes and any maintenance. The reason I do this is for for future reference to compare in case i think there is an issue and because it keeps me close to the compressor to monitor the operation for any issues. Basically so i dont walk away and forget it is filling. The other reason is batteries and tiny cheap meters fail and If i write it down i definately have the info. Just my 2 cents.