Everyone seems to be getting help from the Global 500 these days.

Redwood Systems, which has created a networking system for controlling lights, sensors and other devices in commercial buildings, has received $3.5 million from Mitsui & Co. Global Investment.

Redwood came out of stealth last year and is in the midst of expanding the applications for its technology. The system essentially consists of a centralized computer console connected to LED lights, temperature sensors and other devices in the ceiling of an office or data center via an Ethernet-like connection that also delivers power. (DC power, to be exact.) To save energy, the system can automatically dim lights or warn facilities managers when an AC unit is on the fritz. Check out the video below to watch it in action. (That's a ceiling LED with sensors attached in the photo.)

One retailer is looking at Redwood's ceiling networking as a way to monitor traffic in stores and at check-out counters, CMO Sam Klepper told us in April. If too many customers are waiting in line, Redwood's sensor network could ping someone in facilities or management to open another counter.

Office building owners are also looking at ways of exploiting the technology to make better use of their conference rooms. The network, equipped with motion sensors, will be able to determine whether a conference room is currently being used, as well as whether it is the whole room that is being used or just a portion of it. Historical data can then be mined to optimize this real estate. Another potential application: ambient dust level monitoring for data centers and office space.

Customers include Facebook, Johnson Controls (the building management giant), SAP and Volkswagen. While some customers are installing Redwood's networks to control their office space, data centers are something of a leader in this space. Corporations pay more per square foot to control their data centers, and data centers are also one of the first places LED lights will go because the light from LED bulbs is not itself hot, thereby cutting air conditioning costs.

Other competitors in light networking include Daintree Networks (indoor ZigBee-based networks for lights), Adura Technologies (mostly concentrating on fluorescent lights but with LED capabilities), and Digital Lumens (LEDs in meat lockers, warehouses and industrial spaces). We've been waiting for some of these companies to get bought. Besides curbing power consumption and electricity bills, these networks allow building owners to link their lights into demand response networks. Now, demand response networks largely harvest negawatts from air conditioning systems and heaters. Lights would give them more flexibility to respond to calls from utilities for peak power curtailments.

Mitsui is one of many large companies plunking money into green. Toshiba recently bought smart meter maker Landis + Gyr, while ABB and Schneider Electric have been snapping up large and small companies in the U.S. and Europe at a torrid pace.