I am investigating overheating / cooling whilst we are running tests for VR and 360 recording and streaming because our personal smartphones get hot quite quickly even with an aluminium case and we will be streaming for four hours. You don’t have to use a smartphone for streaming and our tests were using a smartphone with the Vuze+ camera which we will be using with laptop instead of phone. But we are interested to know if there are options for smartphones. If we use something like an Insta360 Air we will need additional cooling options if recording / streaming motion of some kind for at least an hour. (Have not purchased Insta360 personally but may do in early 2019).
A technical colleague suggested some kind of metal plate but this may be difficult if you want to hold the phone or an accessory stick. Some cases appear to be on or nearly available such as Optimal. If a mobile phone could be streaming / recording and doesn’t need to be held, then a mobile fan / radiator may be an option (again not tried but this would be interesting to see how much noise it makes and how it affects the quality). Research includes looking at graphene to cool and I guess manufacturers will continue to look at internal as well as external options as VR usage and streaming increase.
Depending on any fan noise, this looks like a nice idea for temporary cooling, if you are not outside and/or there is a lot of warm air circulation already because the USB powerbank looks quite small and light. Will ask around.