I like it! It's a button-less proximity widget, so I generally have to be sitting on the bike (or very damn close) to test it. But I do believe I can come up with a stop sign or something to test with.
Ah, does the widget use a battery?
Otherwise it's probably RFID like most car keys these days so you may not have much luck with the bike alarm, you may have to try the garage remote instead.
You could also try shielding the transmitter instead of the receiver, may have more luck and may be a little easier ... kind of depends whether the transmit signal is being lost because of the other signal or the receiver's frontend is being overwhelmed.EDIT:
Actually, if your bike widget is RFID that could be a completely different set of frequencies, ie. RFID can be:
•LF : 125 kHz - 134,2 kHz : low frequencies,
•HF : 13.56 MHz : high frequencies,
•UHF : 860 MHz - 960 MHz : ultra high frequencies,
•SHF : 2.45 GHz : super high frequencies
And your garage remote might be 315MHz or 433MHz.
Sounds like something affecting a really wide range, your best bet might be finding a friendly radio amatuer to help. Or possibly the local TV antenna/satellite installer, (with the right gear), might be willing to offer assistance for a beer or two.