They are taking pre-orders for the sensors now, just got my order in
Hoping for mid september, but it depends on if they can get enough pre-orders to buy the bulk order to get them at a decent price.
It's 40Euro including shipping to the US. You have to do the order via their 'Donation' page. I did 50Euro, so a little extra to help out. Seems like an interesting project to me
Bok