Interesting. The protocol TMT, seems to have the idea of users having multiple nodes (which are referred to in comments as devices). I suspect if I were to use this in a product, I'd use nodes for application instances instead, so if a user had multiple apps (i.e. consumer payment app and merchant dashboard app) on the same device I could keep them straight. Seems promising.
(Author here.) TMTP clients maintain concurrent (possibly intermittent) connections to any number of TMTP services, and each service gets its own inbox. So you don't need a separate app instance per service.
Inboxes for a set of related services could conceivably be merged, tho I haven't done any work on that yet.
