Very early stage, and quite speculative -- but promising.

Unique value proposition for a very large addressable market with no apparent competitor.

100% retention. 

Fast growing sales (off low base) from top tier customers.

Well managed costs and ability to scale well.

Recent funding gives path to break even (hopefuly)

Big backlog of installations.

Aside from winning new customers (most of which appear to be inbound inquiries), growth comes from these customers expanding the service within their network, and using more features.

Have taken a small stake here on SM and in my real portfolio.