Recently I've been developing two separate CastMinder systems. The "smart" system is the one I describe in the most detail. It consists of Bluetooth sensor nodes and an iOS application. However, I've also been working on a "dumb" system, which uses RF24 chips to talk to a receiver. The dumb system does have certain advantages, such as the fact that the battery lasts much longer, and it costs almost 4 times less than the Bluetooth system, not even including the cost of a phone.