Proving yet again that there's pretty much nothing that can't be made to work with an iOS device, a product called SwingTIP, on display at CES 2013, creates a link between your golf club and your iPhone or iPad. The lightweight sensor (US$129.99) connects to your device via Bluetooth and sends detailed data on every swing to a companion app, with the goal of showing you what you're doing wrong and offering suggestions on how to improve your game. Hopefully they're more helpful than some we've received over the years.
In addition to working with its companion app, the data produced by the SwingTIP can be uploaded to a website and used to create scorecards. These can be shared with your golfing coach so they can provide further feedback. The sensor itself slides onto a mounting bracket on your club's shaft, and additional brackets can be had for $19.99 apiece in case you don't want to move the one that's included to different clubs.