I realize this is a rather old post… but wanted to reply on this issue: Until we actually try out the unit and see how it is designed, we will have no knowledge of what it is capable of. Humidity will need to be dissipated in some fashion and if it was designed to do this function, I am sure they will have taken this into account.
The issue of how long the batteries in the unit will last and whether they will be replaceable is an interesting one. I have found that three years is usually the point at which rechargeable batteries start to go south. Could be quicker if the unit is not used much or if it is allowed to discharge completely on a regular basis. I use rechargeable batteries a lot in my work (video production) and you have to get in a routine with them to keep them in top condition and even then, they need replacement periodically. Replacement could be a new profit center for audiologists!