I built it last year. It has basic white-label support, but I'd be happy to work with you guys to integrate the UI more closely with what you already have.
I'm working on a better landing page with screenshots; in the meantime here is a PDF with more info: http://www.blackchair.net/hubfs/SMS_Inbox.pdf
I'll be digging into the beta :).
Lots of API goodness: https://textit.in/api/v2
For my current product I'm looking for a human-human SMS interface in a browser. Ideally, it should just drop-in and work.
SMSInbox pulls outbound messages directly from Twilio logs and creates an embeddable iframe interface. Does Textit.in offer similar functionality?
I do have other ideas that involve bot replies but have some concerns due to the complexity of the workflows in this product. There are dozens of variables involved.