Yep, I created Shopkit. The current PayPal integration is there, but I’m working on generalizing the code so that it’s easy for people to add more payment gateways without touching the template code.
Now that I think about it, I’m not sure what benefit a Kirby-focused plugin would have over something like Omnipay. But anyway, I’ll share the code when it’s ready and I’m looking forward to seeing yours!