On-demand babysitters for short errands

My sister, a stay at mom, has an idea for an app for mothers Sporadic babysitting Like Uber But the 'drivers' are a network of young girls available to babysit at a moment's notice And the 'customers' are moms with infants and toddlers who need to run an errand unexpectedly You pay the baby sitter to tag along for the ride and keep the baby entertained while you deal with the pharmacist/grocery cashier/bank clerk/post office attendant etc. I feel like the person who makes this happen could make bank. Call the app "A Mother's Helper"