Riiid is one of a handful of companies that believe that A.I.’s algorithms are perfectly suited to track student performance and give individualized attention.

The company OpenSensors uses small, inexpensive sensors to monitor air quality and other conditions in offices. The timing couldn’t be better.

Waterplan, which has some impressive clients, says it can — and just as water stewardship is becoming increasingly urgent.

The Korean start-up Tridge is working to create a network for buyers and sellers, collecting valuable data in the process.