I use a technology called ZigBee. It's a wireless protocol made for Internet of Things devices. This part represent about 60% of the production cost. This chip is expensive but gives years of battery life.
Curious about what price did you expected?
I expected this to work through either wifi or a very cheap USB dongle. The price point for a base station with one device should be 49.99 and each additional device should retail for 14.99. That's my honest opinion.
This is really interesting to me too. I've been looking at a bunch of technologies to make "jelly bean" sensor nodes (i.e. cheap enough and simple enough that I don't have to think twice about popping one into a project).
Those price points are hard to reach for retail pricing, but are pretty close to the "in bulk" pricing that I've got things down to (once you factor in labour, NRE for solid firmware, etc). If you want a cheap and unreliable setup, you could probably get the node price down to around $5 or $8, but I don't think I'd want to rely on it.
Thanks for the reply. This kind of price can be reach using Bluetooth Low Energy. Those chips are really cheap but as you might know, the range is too low.
This can of course be far from the effective distance, but since the data being communicated is so small it should be possible to keep sending the data until you can acknowledge that it has been received.
Also, you could look into creating a mesh network between all Notifons, so you could extend their range.