I buy my perfect gig calendar every year at Office Depot. It's a big wall calendar. Each day is a block into which I can write the details of the gig. Employer, pay, location, dress, which instrument. It's even my accounts receivable system. When I get paid, I check off the money. It's my tax record for music income, too.
It hangs on the wall in my wife's studio where we both can get to it and see what's on the schedule. When we go out of town together, it folds neatly into a briefcase-sized packet and goes along.
It's impervious to theft, power surges, battery failures, lost cables, and software bugs. It has no monthly fee.
Do you think something like that will ever catch on?