Well, installing Powerwalls in a garage just got a bit easier since we have a heat detector that County of Santa Clara Fire Department will accept in . Even better that it is wireless and interconnected, but it is not cheap. It is listed and can be set for a trigger temperature of 117, 135 or 175F, so the worry about a too high ambient temperature in the garage with the other heat alarm (HD6135FB) goes away.
I just installed a set of these for my personal home, and am so far very impressed.
OmniShield – Welcome to Your Home Safe Network
Before recommending them I needed first-hand experience and I like them so far. I bought 4 smoke alarms, 1 heat detector and 1 CO detector. I also bought the CommLink which allows you to interact with them on your phone through the internet. I can set up to EDIT: 8 contacts that are able to get a text message whenever an alarm goes off in my house. Also, I can look at each individual detector, and see what the smoke level is, how badly it needs to be cleaned, how much battery life is left, and what the approximate air temperature is at each unit. Here is a screenshot of the app interface showing the status of the individual alarm:
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So far the only downsides are the cost, and that the CO is a separate alarm instead of integrated with the smoke units. Interconnection was literally automatic, as long as all units are turned on within 1 minute of each other and within wireless range. Setting up the wifi network with the CommLink took a couple of tries before it all worked. They have a 10 year lifespan and expected battery life at least.
Wireless range also seems pretty amazing. I still get signal in a detached building which is 120' away, and another 30' of distance inside that building. This is with wood siding on both buildings and no windows open. They say the wireless interconnection range is 200' and each individual unit is itself a signal repeater.
Unfortunately, the average consumer cannot buy these off the shelf. They are dealer-installed only but will make a good solution so that our garage mounted Powerwalls are easy to pass inspection.