The Breezi AirPulse is a Bluetooth sensor that you stick in the filter in you furnace and air conditioner. It senses the pressure and estimates the life of the filter.
Clean filters, of course, mean cleaner air and lower energy demand.
The device reports to a mobile app that Charts the filter status and sends a push notification when your filter nears the end of its life.
The AirPulse is slated to be available in the spring for about $30.