Paying for products has gotten more and more convenient in recent years. Credit card companies began by rolling out quicker payment methods like Discover Zip and Visa payWave, services that allowed customers to simply tap their credit cards on a scanner to pay. Then, digital services like Apple Pay and Google Wallet allowed people to pay without a credit card at all, using only their smartphones. Now, a new startup is looking to move convenience one step further by making paying as easy as wearing a wristwatch.