The Planet Waves PW-HPK-01 huminifier is a great idea. Easy to apply and use. There are not much plug-in to do, as it simply goes into the guitar case. So thumbs up for idea and put in use.
The more troublesome part is when to replace the humidity pack. It's indicated to last 2-4 months depending on temperature and humidity. However, it is hard to detect, when it is time. With the price tag for replacements it is rather costfull to use the product - even on a 4 month basis (if you have more than a single acoustic guitar).
Even though, you need to refill the spunge on a weekly basis, the Planet Waves GH Humidifying System is more reliable and way cheaper to buy and use.
If you are unable to care for your guitar on a weekly basis, there is no doubt in my mind that this will be the perfect solution for 3 month running periods (guitar stored in house in a normal temperature and 'moist' environment).
