We are planning to add Apple Pay support to the Expend in the near future. As we see it, there are two stages:
Stage 1: Being able to top up your Expend float account with Apple Pay, using an existing card linked to it. This is a shorter term plan.
Stage 2: A fully-fledged integration with Apple Pay so you can pay for things using Apple Pay and it comes directly from your Expend account. This requires a rather involved process with Apple and we hope it isn't too far off. It's definitely on our roadmap.