I would say that this particular item is a little gimmicky... no interest from me (and I live in the tropics)... But... I would say that a good dehumidifier is invaluable.
My own dehumidifier is a a 2yo 450l upright freezer that the missus tried to put a latch on... she drilled into the condensor. Ouch!
Eyeing the thing one Sunday afternoon... and muttering a few choice words
... it hit me. A new condensor (mounted internally with some ducting and a circulation fan) and a regas and I was on my way.
It holds everything. At the end of the day, I simply stuff my camera bag in there as well. If I am away for a couple of weeks, I am not going to get so worried that I am going to want a portable unit.
Cheers