Both devices let you wear your iPhone as a supersized pendant/necklace but the iDangle also can include earbuds, making it easy to answer a call and listen to music while walking, etc. The iHangy doesn't protect the actual phone, but on the plus side, it can work with most third-party cases.
A ton of folks have asked me where I got mine each time I wore one of those devices. But the ladies have had issues with the length and, ahem, chest placement of the iDangle.
The iHangy might be a better fit, literally, for women. The chrome and silicone design makes it stylish, and it connects to the iPhone's 30 pin connector. This might seem like a concern, but it is quite rugged and doesn't come off unless you deliberately squeeze the ends of the connector.
Those ends also serve as a double-sided stylus, reminiscent of Darth Maul's light saber! The silicone necklace is available in white, pink, or black, and can be fairly easily adjusted in length. The iHangy is also available in a chrome keychain clip.
At $13 for the necklace and $10 for the keychain version, the iHangy is a nice option and makes a great gift. I would still like to see integrated earbuds, as the iDangle offers.