Things will often communicate directly with other things. Take for instance a thermostat that adapts its behavior based on heat sensors in different rooms. Things will also sleep to save batteries. A device might wake up and gather some data and go back to sleep again after having evaluated that data. Radio signaling requires a lot of energy so the device will only connect and sent data when it is necessary, to save battery. This means that the communication will be bursty in its nature.

If the “listener” is also running on batteries, it should also be asleep when not in use. Neither the sending or receiving device should be required to stay awake and wait for the other one to wake up before signaling since that would reduce battery life. Ideally the communication should be asynchronous, like e-mail or messaging, instead of synchronous, like a phone call where both are online at the same time.

A secure connection will require strong encryption since the communication is outside the protection of traditional firewalls, and that is heavy on processors. Unnecessary signaling of raw data draws battery both for the encryption process and the radio connection, so if you want the device to have long battery life you need to design the device with some intelligence that makes simple decisions, like “tell the heater that this window has been opened if the temperature is below 15 degrees”.