There are two parts to these devices. 1) The plug adapter, which is just that. It will convert a two-prong US-looking outlet to a 2-pole outlet that you would find in Europe. 2) A power converter, looks like a small brick and can be used to convert power down from 220 (EU) to 110 (US).

Most high-end electronics devices can support world-wide power sources (110-240) assuming you have the correct plugs. For these types of devices, you can't use a power converter, JUST a plug adapter.

Lower-end electronics; hair-dryers, clock radios, etc. usually cannot support non-US power sources. Things like hair-dryers tend to have too much of a draw for power converters and can run really hot.

You're digital laptop/camera will most likely be fine. If you give me the devices, I can help check the specs. Your travel hair-dryer/curling iron may not do so well, and cannot use the power converters; too much of a draw. That said, many of the big name hotels abroad, have a 110V US-style outlet in the bathrooms.