The key thing is what the transmission frequency is - if its infra-red then it is almost certainly not going to work if there's a wall in the way. If it's radio then it may do, but depending on the frequency it could get or generate interference from all sorts of other things.
I'm expecting the technician at 3 pm. Will give you an update when it's done. I'm hoping it will work! We're trying infra red ... and there are walls ...
Update ...
The result was not satisfactory enough. The technician actually turned up with the radio device (not the IR because of the walls). Transmission was unstable. Overall, it was very good but it could be affected anytime by interferences.
I was not ready to put up with this. The shop owner has been great. He took back the device, didn't charge me anything and even apologised because he could not find a solution.
I guess I'll have to get a 2nd box from NOW if I want to watch on the 2nd tv. It costs a little bit more than $100 for the same channels to which I'm already subscribed AND I can watch different channels at the same time.
If anyone has other solutions, let me know!
I tried and bought an IR video sender (2.4ghz) got at Mongkok computer center. The image is very good (no loss of signal at all), but unfortunately the sound is very soft. In the end, I had to hook up a pair of speakers to bump up the volume, not ideal but at least it still works, coz we only need it for like 1 hour a night for my parents. To change the channel, we have the powermid transmitter which we brought along with us from UK, works like a charm.