Sensors definitely increase the acquisition costs, although at least early on there's customers who see them as a benefit they're willing to trade the usual cashback/discounts/etc for, so its not as bad as you might think. We're also looking at ways to reduce the cost of sensors over time.

As for proving that sensors mitigate losses, even in our initial beta period we've seen a couple of potentially large escape of water claims avoided by early detection of a leak, and that's before we start introducing truly preventative measures as opposed to just detection. We're very focused initially on escape of water because those are in fact the largest source of losses in the industry - fire is fairly rare, theft tends to be pretty cheap to handle claims for, but a leaking dishwasher left while someone is at work for the day can easily require replacing everything on the ground floor of a small house.