This is what I came up with for Owe.to:
Forms that are conversational come with a unique set of issues that you need to deal with to make them usable for the user. For one, they don't have labels, and the user has to figure out what he needs to fill in based on the context. I came up with a way to provide additional context using a sort of dynamic label that I call Callout Labels that appear when the form field receives focus (think this evolved from a tooltip suggestion by Jinesh):
How about help text? The traditional way of displaying help text around the form field was not feasible, so I had to display greyed out help text inside the form field itself that disappears when it receives focus (look at the previous two images). Although this technique is wide spread (for example, in search forms) it hit home in the context of Owe.to when I came across Twitpay:
Another interesting issue is figuring out how to display validation errors. I'm not there yet with Owe.to, but I like how Huffduffer does this:
