The selection of standalone Pocket PCs (and add-on cameras) has really dwindled and most have cell phones built-in. Are you open to those with phones built-in? If so, there's quite a selection to choose from.

If not, the discontinued HP rx3715 with an external Bluetooth GPS is probably the best fit since it has a camera and WiFi. http://www.mobiletechreview.com/iPAQ_rx3715.htm .