Scheduled for release this month, BiKN uses 802.15.4 — the basis for ZigBee, among other low-power wireless network protocols — to pair up your iPhone to a bunch of tiny tags that can be used to locate objects that you attach them to. The system is facilitated with a special RF-enabled case that you slide your iPhone 4 (or iPhone 3GS) into; after installing the BiKN app from the App Store, you can choose tags that you've paired and find out how far they are from you with a range up to several hundred feet. The tags themselves, each the size of a matchbox, are rechargeable (they're supposed to last a few weeks) and can beep so they're easier to find — the iPhone gives you a radar-like indication of how many feet away you are while the tag itself is making sound.
What's BiKN useful for? The sky's the limit, it seems — anything that you need to track within a short range, BiKN looks like an interesting option. Attach a tag to your keyring, for instance, and your keys become a lot easier to find if you've got your phone; put one on your pet's leash and you'll know when they've strayed too far. Likewise, the iPhone case itself is a trackable tag — pair two phones together and they can be tracked from one another. The case and the tags all recharge via Micro USB, so there aren't any proprietary docks or connectors to worry about (though you'd need to remember to charge your tags periodically before they go silent).
The system will be sold in a couple packages ranging from $100 to $120, while extra tags will be sold in two-packs for $50; the system can support up to 256 paired tags at a time.