I'm becoming more and more in love with my iPhone's camera as the days pass, especially when apps like ColorSplash come along. ColorSplash ($2) allows you to use your finger as a brush, and color in or grey out any part of your photos you choose. This effect is really cool when you have reflections, or interesting objects within a photo that might have otherwise been missed. Plus, ColorSplash allows you to zoom in and out using the iPhone's multitouch technology to get really precise strokes.
After making your changes, you can save the photo to your iPhone's photo gallery, or if you want to really take your time, you can save your session for later. I took this photo at a local coffee shop, and am totally thinking of starting an iPhone ColorSplash photo group online.