Glen Fleishman, with a little help from Josh Centers, walks through the payment apps that work inside the iMessage infrastructure. Learned a lot, all very interesting, but found this telling:

We’re still in the early days of iMessage apps, but two prominent payment apps have added iMessage integration: Square Cash and Venmo. A third, Circle, was launched on multiple platforms by entrepreneurs with deep Internet roots. Oddly, PayPal hasn’t yet updated its app to support iMessage payments, but the company often lags putting improvements in its native software.

Is this a wait-and-see on PayPal’s part? They’ve clearly opened a door to the competition. Or perhaps iMessage support is just not that big a deal in the larger world of payment processing.