Not all propulsion companies are trying to revolutionize engines for launch vehicles. There's a growing number of astropreneurs who see opportunity in providing increased orbital capability and control for nano-satellites.
Attitude control, station-keeping, collision avoidance, inclination and orbital modifications - if your mission needed any of these capabilities, just 5 years ago you would be looking at a much larger satellite platform and much more cost. Thanks to the work of the 5 companies below (and many others in the NSV Database), the kinds of missions cubesats can undertake are being transformed.
Accion Systems - Developing advanced electric propulsion for nano-, micro-, and miniature satellites.
Exotrail - Selling nanosatellites that utilize Hall Effect Thrusters "HET" and constellation management solutions
Thrustme - Specializing in nano-satellite ion-propulsion and precision attitude control
Phase Four - Developing plasma propulsion technology for satellites
Benchmark Space Systems - Building a low-cost propulsion system for the rapidly growing small satellite market