With the proliferation of hacks for Apple's smartphone it's hard to keep on top of what's most impressive, but we've a feeling that putting Expose onto the iPhone 3GS makes a decent argument for being near the top of the list. It's the handiwork of Steve Troughton-Smith, who you might remember from first identifying the iPhone OS 3.0 tethering hack and then going on to jailbreak the CDMA Palm Pre.
Update: Tom of Ocean Observations, a Swedish design firm, has been in touch to let us know that the original idea for Exposé on iPhone emerged from a video concept some of his team came up with. Check out that video after the cut.
Video demo after the cut
Steve has also developed a version of Stacks for the iPhone, though it doesn't seem like the current version has Expose support quite yet. Still, if you've ever wanted pop-up icon arcs like you might find on an OS X desktop then it's a nifty mod to your iPhone; you'll need a jailbroken handset, naturally, and right now it's on limited alpha release.
We're not sure when Expose will get added - we're waiting for Steve to get back to us - but if Apple aren't going to add desktop-style functionality to their smartphone then we're glad third-party devs are going to the effort. Video demos below.
Ocean Observations concept video: