I just sold some altcoins for LTC using free desktop product called Open Bazaar. They let you accept various major crypto.
I don't know how you did the Walmart API thing for $15 Subway Gift Card, but having a way to buy products & services within wallet would be cool. You already have IPFS which is neat idea. Gift cards, but digital would be even better. No shipping fee. Since crypto is secure one-way, digital gift cards would be a no brainer. There's no risk to the seller and funds are guaranteed.