Stepping Stone's Lightning Trigger at $380. Just lightning, nothing else.
Right, hands up who's looking to spend their Chrisnukah pennies on a neat and groovy photography toy? Yep, just about everyone. There's a surprise. You know what is a surprise, though, it would seem that the adage that you get what you pay for doesn't necessarily hold true for camera lightning triggers. If you're in the market for a lightning trigger, there's a goodly selection of them out there (and what with 2012 supposedly being apocalyptic or something, you'll get plenty of use out of one, I'm sure), but as this rather convenient comparison table shows, spending more won't necessarily get you more.
The cheapest and the most expensive - the Stepping Stone Lightning Trigger at $380 and the Ubertronix Strike Finder at $110 - both respond to flashes of light and that's pretty much it. There's no sound trigger, no motion trigger, and nothing so exciting as a time-lapse feature.
Ubertronix offers two higher-specced versions of the Strike Finder, the Pro and the Elite, at $170 and $350 respectively. You'd think that the Elite version might be all-singing and all-dancing, but you'd be mistaken. It might respond to lightning, lasers, sound, and motion, but it can't do time-lapse. Funny, really, when the Pro can manage time-lapse and react to lasers, but sound and motion are out of its comfort zone.
Oddly enough, the most comprehensive trigger out there is at the cheaper end of the spectrum, costing $150. It's the Triggertrap, and not only will it respond to lightning flashes, laser beams, and sound, but you can deploy its time-lapse feature and it comes with an auxiliary port, too.
Dreaming Robots' Camera Axe starts off as a basic box to which you add your own components allowing you to build exactly the trigger that you want. It starts at $185, but by the time that you've added a cable and at least one sensor - one that responds to lightning, for example - you've spent close to $225. Add a motion sensor to that and you're looking at $245.
Of course, for the ultimate in geekularity, you could always build your own, completely, utterly, and totally from scratch. As in, printing the printed circuit board yourself, programming a microprocessor yourself, and buying all of the components that you'll need and getting out your soldering iron to assemble it yourself. Heaven only knows how much it'll cost you in components and time but it'd be yours. If you fancy doing that, head over to diy-doc.net and look for the SmaTrig 2.1.
Sure, if you only want to photograph lightning, why spend more than $110 on the Strike Finder? But are you certain that you're never going to want to try some laser-triggered photography, or something sound-reliant? No, I didn't think so. And I definitely can't justify $380 on just a lightning trigger.