Using Airplane mode will certainly prevent any charges while still allowing you to listen to music, watch videos, play games, or read books that are stored on the phone or take photos or videos using the phone's cameras. Using Airplane mode also dramatically extends the phone's battery life. On the other hand, I believe putting the phone in Airplane mode will also disable all wireless connections, including WiFi. In other words, you will have to take the phone out of Airplane mode if you want to use a WiFi connection to which you may have access at some point in your trip such as a free WiFi hotspot at a hotel or coffee shop. As others have already pointed out, however, you can still do this safely while avoiding data or phone charges. I was able to make use of a free hotel WiFi connection in Bali last year to retrieve my email and surf the web, and I incurred no data charges.