Thank goodness I am so past the stage of running kids all over hell's half acre for extra curricular activities. I'm not so sure mom's will appreciate the name Dad's Cab, so the company has a "Mum's" version and "Family" version, but they will certainly love the concept.
Attach the gadget to the minivan every time the kids pile in. When the running is done, you hand over a card that says "you owe me a beer" or "mow the lawn" or "you must attend one meal without texting." This is ingenious!