Blue Sky Ideas:
Cellular reproduction:
Most notably a cell which has the ability to pass along any “learned” behavior which can be beneficial in the current environment. For example, a cell which passes along an “immunity” to a specific virus.
Traffic
Possibly, aggregate wait times vs distance traveled could be used to determine flow of traffic. Lights would be required to communicate with each-other. Communications would have to occur at a quicker rate than traffic to be effective.
Cellular emergencies
Cells that operate like the brain/body during emergencies. When an emergency occurs, “assets” will be diverted from less important cells to vital cells. For example, when a person's blood pressure drops, sensors in the blood vessels send signals to increase their heart rate but constrict blood vessels supplying the less vital organs so that the vital organs are more likely to receive the precious asset(blood). Perhaps this could be combined with the cellular reproduction idea dependent on the level of complexity for each.
Cell membrane: