This is just technical information. Most of the sensors/actuators are available from hardware vendors pre made, kits or bare boards.
1 Wire Devices is a line of IC's from Maxim. The idea behind 1 Wire is that you can create a sensor network using ordinary telephone cords (though for larger networks CAT 5 is recommended). Typical applications only requre 1 Wire for data, there is also another one for ground, but in ground plane design that wire is not counted.
Each 1 Wire Device as a unique serial number assigned to it (much like a MAC address on an ethernet card). Also with in ROM of the device is a device type, a family code that can easily be referenced to what the device is capable of doing.
In choosing a 1 Wire design, it is just a matter of plugging in sensors and modules as the user chooses. There is no real limit of number of ports other than physical properties of your wiring, network size (such as delays over long distance), and speed of your communications.
Here is a very good basic explanation of how the 1-wire network funcions. It explains the conceptual basis for the 1-wire microlan.
Here is a handy table of 1-Wire Devices:
I've successfully tested the interface for ph/orp/salinity, not with the probes yet, but the actual part that gives me the readings. Temperature sensors, a digital switch (which is the base for turning things on and off or input such as a float switch), and a light sensor.
1 Wire is the Maxim/Dallas name for their MicroLAN technology.
COnductivity aka Salinity
TEmperature - Tested and working.
PhotoRadiation - Tested and working. I used: