You know the drill: you're recording some video of the kids doing something cute, when suddenly you realize you're about to miss a snapshot-worthy moment. Alas, Apple's Camera app locks you into one mode or the other--you can't take a photo at the same time you're shooting video.
Luckily, Camera Duo can. This 99-cent video recorder includes a button that instantly captures a photo while you're recording. This is pretty cool, though you'll have to live with a few limitations. First, photo resolution is limited to the maximum resolution of the video recorder: 1,280x720 on the iPhone 4, 640x480 on the 3GS. The resulting snapshots are OK for viewing on your phone or a Web page, but definitely not great for print.
Second, Camera Duo offers two photo modes: Real Photos and Extract from Video. The former delivers the better quality of the two and supports the iPhone 4's flash, but produces the camera-shutter sound every time you take a picture--and you hear that sound in your recorded video. Extract from Video eliminates the shutter effect--at the cost of lower-quality pictures and no flash support.
Obviously, the ideal would be Real Photos minus the unwanted sound effect, but we suspect there's a reason Camera Duo can't do that. (It would also be great if it could manage higher-resolution photos, but we know why it can't do that.)
As for extra features, the app lets you choose between fixed and continuous focus, exposure, and white-balance settings, and has flash/light controls for the iPhone 4.
Although our testing was limited to the iPhone 3GS, Camera Duo performed admirably. Snapshots clicked away instantaneously, with no interruption to the video and no delay in processing everything. The results appeared in the Photos app just as though they'd been taken with the Camera app.
It's not perfect, but for the moment, Camera Duo is the only app that adds snapshot capabilities to your iPhone's video recorder. Well worth 99 cents.