Is it possible for someone to remotely/covertly scan for Bluetooth devices? If so, what is the operational range of this scanner?
My concern is that a Bluetooth based door lock will emit a signal that will draw too much attention to my home.
As far as I know the range doesnt depend on the device scanned, but on the device that is scanning. With an antenna it is possible to detect a class 2 device one mile away if you point your antenna in the right direction.
Anyway the question is about wardriving for bluetooth devices. You can use Bluediving loop mode for that (see http://bluediving.sf.net) and I suppose the range will be 100m if you have a usual class 1 device in your laptop. Of couse you could possibly use the greenplague mode and attach a dozen of antennas at the same time. Please send a picture if you do so ;)
If the device isn't normally discoverable, it won't necessarily transmit unless a paired device transmits to it first (depending on how it is implemented.) Range will depend on the devices involved and if you need one or two way communication.
It's also worth noting that even if discovered, a bluetooth lock is unlikely to draw additional attention to you. It is far more likely to discourage attention. When using secure pairing and encryption, if properly implemented, it should be far harder to bypass the bluetooth lock than almost any normal lock (assuming it doesn't also use a pin and tumbler, which is generally fairly trivial to bypass at the consumer level.)
The only information I could really see it leaking is that you are a geek and thus there may be goodies inside, but that isn't necessarily a safe assumption to make either, so I personally wouldn't worry too much about it as long as the lock is proven to use secure pairing and an encrypted challenge/response that is replay proof.