Ditto to Andre's post. My wife and I both used the n'Lock stems on our recent tour in England and Austria. I can't speak highly enough of them. Besides the obvious security feature, they enable routine rotation of the handlebars for parking, shipping the bike, etc. However, there are some issues you should be aware of:
1) There is a slight weight penalty. They are solidly built in order to achieve the desired protection, so they're heavier than a normal stem with identical dimensions.
2) You can't access the top of the stem for The Plug or any other stem-top device. The stem cap is an integral part of the stem and can't be removed.
3) There is a slight side-to-side play in the locking mechanism (less than 1 degree?) which is very minor and has no impact on control, but is slightly disconcerting. I actually hadn't noticed it until Steve at SJS pointed it out to me as he was mounting Kav's stem. He was familiar with the n'Lock, but claimed this play was the reason they didn't offer the stem as an option in a bike build. They believed the customer would not accept it. As I said, it is barely perceptible and has no operational impact.
4) Obviously, you should pick your n'Lock model carefully - I think there are eight models, four "plus" series (accept locking cable) and four "classic" series (no cable locking). Each series has adjustable and non-adjustable versions in each of "standard" and "oversize" handlebar sizes. There may still also be some colour options.
Actually, I think the SJS listing may be in error. It is for the 402 model (as illustrated), but then says "N'Lock 402 Locking 1 1/8 Inch Stem +/- 6 Deg - 31.8 mm Clamp - 100mm" (my underline). I don't believe this model is adjustable. It is a "plus" model, however the listing doesn't mention this important feature. In any event, I reckon the price is great - about half of list! I'm tempted to buy one for my commuter bike.
My wife and I routinely locked our bikes together, and usually to a stationary object, by using one n'Lock cable, and one Abus 4850 frame lock cable. The rotated handlebars allowed for a tight side-by-side fit, and pitlock skewers provided additional peace of mind. Highly recommended if you don't want a nasty surprise ruining your tour!
Sam
