Our next version of BizTalk360 (version 7.1) is just round the corner. We are adding one key functionality in this version called "BizTalk360 for Managed Services". This is primarily designed for consulting companies who work with multiple BizTalk Server customers, allowing them to access all of their customer environments from a central place.
We have taken advantage of Windows Azure Service Bus Relay and Windows Azure Active Directory (AD) to make this thing work seamlessly.
This functionality could be useful in various other scenarios as well, example for customer who have environment spread across multiple places (anywhere in the globe) and they wanted to manage it from central place or for companies who wanted to allow their employees to access their BizTalk environments from public internet (in a secure way) without investing too much in infrastructure requirements like VPN.