I own 4 of these units as well and love them. As I understand it the 3.5mm input jack can be used for external switches like for instance you have a switch on a misting system if your reservoir runs dry. You can't however use it for any powered switches. The data jack says it's for "future use. My guess it was intended to be able to connect online to check or change settings however as far as I know at this time you can't do that yet?. I like the fact I can have one unit to control all aspects of my set ups from lighting to heat to humidity. I also like the fact that these units were designed that if they ever fail they have a fail safe , which means the device they control will turn off so there is no chance your animal will ever get burned. They also have build in alarms. They will not wash your dishes or clean the windows at this point but leave it to spyder robotics and I'm sure they will figure it out! Lol. I can't say enough good things about this product.