The goal here is to keep all valuables on you while traveling. But keep them concealed so you'll look like a local. I don't travel with a lot of technology. I keep my laptop at home and strictly use my smart phone while overseas.
Dedicated Compact Camera - I currently recommend the Sony RX100 (any in the series) as a compact point and shoot camera. It takes great pictures, shoots in RAW for better editing, and fits easily into any pocket. Cellphone cameras are great for quick photos but when I want to capture memories, I'll still bring my dedicated camera. Point & Shoot cameras are relatively inexpensive in the off chance that it gets lost or stolen. And in the end I still feel that they take better photographs than smart phones, especially in low light situations.
External Battery Pack - This ANKER battery pack came in so handy on my 2013 trip. Adam brought it along and it was used to charge our cellphones a dozen times. This model has 2 fast charging ports. This is a must for when you're stuck in an area with no convenient electrical outlets like an airport, airplane, or hostel.
Cellphone - These are a godsend when planning on the fly or tracking down that hard to find AirBnB location. I've been in scenarios where hosts have canceled last minute which have left me with no place to stay. However the remote power of the cellphone allowed me to book another place to stay without skipping a beat. There are also apps that allow you to purchase train ticket at a considerable discount rather than paying at the station. You can pick up SIM cards at your destination (usually in airports or train stations) and have them activate the card while there. I usually stick to mainline providers like Vodafone or T-mobile however shops like Tesco also provide cellphone service but activating can be tricky.