I would assume that if you could get root access / system administrator login on the station's computer system, you could make it send whatever you wanted to. A test signal perhaps.
I would consider using an unprotected wireless LAN access point instead of Bluetooth, many people don't think to set a password on those... it could just be "password" or "0000" etc... W-LAN has a longer range as well and no pairing etc. enters the picture. How you would get root access on one of the PCs on the LAN from the wireless, I don't currently know but it might be possible to use some kind of packet sniffer, port knocking, etc. software and brute-force some service running on the target, such as SSH or an HTML server (Apache?) that requires an open port. Depends how good the target's security would be. On an amateur station, it might be possible.
This could be done from a car parked nearby, from the sewer system, whatever... would only need the necessary knowledge.
Explaining this would need some technical knowledge to get it right and make it sound plausible.
Edit: Or if your hacker has the right connections, acquiring knowledge about some kind of zero-day exploit (hitherto unknown security flaw) in the operating system running on whatever the target is, might be possible too. This is not an everyday thing by far, though. Depends who the hacker is.