allow configuration of a custom online payment URL
It would be awesome if Xero allowed you to setup/integrate a custom "online payment gateway".
At the moment, Xero allows you to include a link in your invoices that connects customers/clients to a PayPal page to make a payment.
What would be fantastic is the ability to include these links and accepted cards logos, but with a link to a custom gateway that includes a variable - such as the invoice ID or something.
In our particular situation, we have a payment system hosted on our website at https://pay.ourdomain.com/ which accepts payments from our various in-house applications. To be able to include a link in Xero that was something along the lines of "https://pay.ourdomain.com/index.php?type=xero&invoiceid=" and have it append the Invoice ID on the end would really sell this product for us by letting our customers make quick and easy payment through a gateway they are familiar with.
Xero supports custom payment URL to power the Pay Now button on invoices sent from Xero.
http://developer.xero.com/documentation/api-guides/payment-services-integration-with-xero/