https://stripe.com/us/help/pricing
It's interesting that the fees are the same for a transaction when a card isn't present 2.9% + 30 cents, but 2.5% + 10 cents per transaction when a card is present.
I wonder what Stripe's response to this will be.
Edit: OK, it appears they give you a slider.
With Android, Google provides parts that different device manufacturers can use to augment their device. Manufacturers can use their own hardware and add whatever software they want to Android.
Not a great analogy, though -- especially since my initial impression was that it only worked on Android while Square was for iOS.
A better analogy would probably be "Stripe's API + Square's Hardware".
They feature a Stripe integration of some sort.