Can i rig this thing to open and close relays in a programmable logic controller? Either that or get some band of output to send a control signal of some kind through a parallel port?
Yes, of course! The Muse SDK provides EEG power band data. There are many ways of connecting software outputs to hardware. For instance, you could connect to Muse with a computer and then send commands to a microcontroller over a wire or radio, or equip a microcontroller with a Bluetooth interface and directly connect to Muse using the Muse communication protocol (https://sites.google.com/a/interaxon.ca/muse-developer-site/muse-communication-protocol). You will likely also have to build a driver circuit for the relays, depending on the type of relays you choose to use.
Is there something specific you have in mind?