[junkcollector]

Medical is just an example of the economist not understanding the product vs the buzzline. It is a terrible tech implementation for medical, but I agree that you generally want medical encrypted. However, if you are talking medical, the cost of the sensor device is tiny compared to other costs even for very expensive sensors.

Fuse based programming would have a whole host of issues. You either need a destructive fill device or load at the factory. If you load at the factory you have to trust them to not retain copies, keeping in mind that it will probably me manufactured in China. If you use a fill device you open up for destructive programming (IC fuses) you open up a bunch of liability for accidental damage to the device plus the cost of a technician plus training can quickly swamp out the cost of your low cost sensor network.

Finally, these sorts of networks work best with asynchronous uni-diretional communication applications. This makes good crypto-practices very difficult. If you chose full crypto and handshake protocols, the amount of data you spend just exchanging keys and handshakes will exceed the data the sensors collect.