433MHz coupled wireless smoke detectors are about as cheap as ones without. And their signal can be intercepted by a cheap Rflink device: http://www.rflink.nl/b

433MHz coupled wireless smoke detectors are about as cheap as ones without. And their signal can be intercepted by a cheap Rflink device: http://www.rflink.nl/blog2/devlist http://www.rflink.nl/blog2/devlist Granted they are not as fancy as a Nest, but you can buy 5 of these for the price of 1 Nest. And the Nest's aren't flawless either. I've had to reconnect 2 of the 3 Nest's at my parent house multiple times now and also a Google account is now required.