Anytime you leave your provider's area (they should provide a coverage map), you will be roaming (this applies to both data and voice). International roaming is very expensive. In order to avoid these fees, I highly recommend that you disable roaming and/or data within your iPhone's settings...regardless of if you have iCam on your phone...because other apps use data, as well.
When you get to your international destination, find and connect to an unsecured wi-fi network (or a secured network preferably...if the password is provided)...then you can use iCam (and other apps...nearly all of which use data). This way the data is being transmitted by the wi-fi network, and not a cellular network.
If you do not disable data before boarding the plane for departure (Settings > General > Network > disable "cellular data" & "data roaming"), your phone will definitely use data (even if you don't open any apps)...and it will be a nasty surprise on your phone bill. Disabling data does mean that you will not receive motion event alerts while you are traveling (except while connected to a wi-fi). If you haven't already installed/configured Dropbox to work with icamsource, you should do that...it's free and will back up your motion events offsite (in the "cloud") in case your computer is stolen while you're gone.
