In today's digital world, debit cards and mobile banking apps are replacing cash allowances for kids. Startups are racing to corner the market, offering chore, savings, and even investment features.

We're talking, of course, about debit cards for kids, which have evolved from a humble piece of plastic into a powerful digital tool that can teach your kids how to make the most of their money.

Most offer physical debit cards and ways for kids to save, while others boast financial literacy lessons and investing features as well. Since federal law prohibits children under 18 from opening ...