Also, https://walla.by/the-wallaby-card - they have been around even longer.

I think Wallaby works differently by being a new plastic card you use and they dynamically route your charges to which ever registered card will give you the best return (cash back, airline points, etc).

I've been using Wallaby for a while (the company I used to work at invested in them).

They're really awesome.

I haven't used Coin or Echo for comparison, though.