Buy a good one first and foremost. These two links will help you in the right direction. General alarm disk lock verdict ? General Motorcycle Forums & Chat | MCN Motorcycle News Showcase: Disc locks - Product features - Visordown Locks & Chains reviews - Kit - Visordown
Not alarmed but I've got a roadlok for my rsv4 and just ordered another for my hyper RoadLoK - Simply Secure Not cheap but definitely the best.
I've got an alarmed Oxford one, less than a year old. It's been dodgy from the start. Doesn't alarm arm alarm and sometimes it difficult to set. But once you do get it working its a solid bit of kit. The alarm is nowhere near as loud as the immobiliser alarm, but it's a second line of security for me. Use it in the rain all the time without any issue. Dunno how much it costs as I got it for free with my bike magazine subscription.
