Ask HN: Mobile shopping cart recs?

Looking for mobile shopping cart software I can integrate into an existing web site. Seems like there are lots of options for uploading product to a hosted store, but we're struggling to find a good mobile shopping cart solution with strong APIs. The important part here is mobile.

We have customer specific pricing and real-time availability is also important so it needs to be heavily API based rather than turn-key "populate the product DB and off you go".

Any recommendations?