A lot of people already have an iPhone, so leveraging that existing infrastructure costs $0.
It'd be pretty easy to have the thing speak bluetooth and write software to communicate with any phone or computer. I imagine the choice to make it an iphone accessory was a marketing-based one, what with the name and all.
Technically easy, yes. But Global Bluetooth certification is prohibitively expensive. We chose to make it an iPhone accessory, because we think it makes a lot of sense to have a nightstand charging dock (which is where most of the cost comes from) and this wake-up feature in one device.
In software, yes. In a separate device for $70? not so much.
If we get to really high volumes, we can probably reduce the price. Remember, we're just a small operation working on a launch. Tooling for injection molded parts is pretty expensive. If we ever get up to many thousands of pieces, we may be able to get the cost down to that of any charging dock...which again is where most of our costs lie. The motion sensor and lens are very advanced, but they are pretty cheap due to their very widespread use in other products.