Six months ago I didn't know any companies pursuing this opportunity, even though some of them have been at it for a while and have successful implementations to point at. Now I fall over them all the time, and suddenly the industry mainstream, including proper grown-equipment vendors and even network operators want to talk about this.
The company du jour is Senaptic, which has just come out of stealth mode, having been incubated within equipment vendor Plextek. The latter is precisely one of those companies that has been ploughing the low-power IoT furrow for years - 25, to be precise. Its technology is deployed in the LoJack vehicle tracking system, in a smart parking system in Moscow, and is also used by Telensa in supporting smarter street lights in British cities.
Unlike fellow low-power wireless provider Sigfox Senaptic aims to be a technology provider, not a network operator. It plans to sell systems to organisations (mainly enterprises, but also local authorities) to use for their own purposes - tracking, monitoring, controlling, whatever. So there is no need for the kind of OSS that a public network would require, to provision devices, manage their subscriptions, bill for usage etc.
But it's not 'merely' a connectivity play - it also offers a platform that does include an OSS, applications, and of course devices.
At the moment Senaptic has only six employees, though the system is still supported by staff within Plextek. In the slightly longer run it aims to have about 100 people.