Use a high setting on your camera phone. Use a regular camera and zoom in. If it's for the outside menu, it's fairly simple. If it's for the inside, it's still possible. I handle the account for these with ACE and the photos people get are pretty amazing most the time. People can also write down the prices, but that takes longer, hence the photos. Some people say they're taking photos for co-workers so they'll know what they can order and the prices. Or for a party, business meeting, college essay, whatever.
I suppose this isn't for those who are shy, nervous, or timid. The guilty look on their faces would probably give them away. However, I have been in many, MANY stores and I'll take photos of products I like for future reference to either buy or, in cases like jewelry, to make for myself. Never have I been caught or asked to stop. If they ever come to my area, I'm taking these without a second thought because I've had plenty of personal practice.