This is cool marketing but it is way expensive than I expected. I am not sure pricing is DIY-friendly but you would certainly find people to buy that.
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.
http://stackoverflow.com/questions/14136218/bluetooth-mesh-n...
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.