I want to thank everyone who provided input for this thread.
With the Rain8 systems, I am seeing some options that the one way controller has that the two way doesn't. I am also seeing some limitations that both of them have such as no display for local configuration. Instead you are required to connect the unit to a serial port for configuration. With all of this information, I think I am going to opt out of going with the rain8 system.
I do have an electronics background and have done some work with micro-controllers (PICs). I am thinking of designing my own sprinkler controller and incorporate the best of all options. Below are the options that I propose to incorporate in the unit.
1. 8 switched zones with 24 volt AC output for valve control. Each zone will be controlled by the micro controller and can be set active or inactive. The user should be able to store a name for each zone with a maximum of 16 characters. This zone name will be displayed whenever a zone is actively running.
2. 1 master valve/pump start control line with 24 volt AC control. The master control line will be controlled by the micro controller and can be set to activate whenever a zone is turned on, or used as an additional zone.
3. 1 rain sensor input. The rain sensor will connect to one of the micro controllers IO ports and be able to be configured to use either normally open or normally closed rain sensor switches.
4. Each zone can be assigned an X10 address allowing the user to manually control each valve through their home automation control software such as ActiveHome Pro, Heyu, or other such software. The X10 control for this would be provided from a TW523 two way powerline interface.
5. Each zone can have a maximum runtime set as a fail safe so that in the event that an X10 off command is not received, the zone will shut off automatically if the max runtime is reached.
6. The controller will have a built in programmable real time clock giving the user the ability to program a set schedule for up to 4 zone cycles. This will be an automatic mode that will allow the unit to run stand alone without the need for Home automation software.
7. The user should also have the ability to set basic schedule parameters such as maximum zone duration and the number of sequence repeats up to 4. For example, a 4 zone setup with a max zone duration of 15 minutes and a repeat of 3 would cycle each of the 4 active zones for 15 minutes each and then repeat this 2 more times.
8. The user should also have the ability to set advanced parameters allowing for individual zone runtime durations and an optional pause time between the start of the next zone.
9. In automatic mode, each zone that has an X10 address assigned will send on off signals as each zone is turned on or off to update the users home automation software setup.
10. The system will have a 4x20 LCD screen with 4 buttons for programming and data display.
If anyone can think of any other useful options that I may have missed in the above outline, feel free to chime in.
For somewhat rapid development of this I have a couple old OOPIC micro-controller boards laying around doing nothing that should be able to get me a functioning unit with not too much effort. I have already ordered a battery backed real time clock module that will provide the timing control. The hardest part will be the programming.
Again, many thanks to everyone for their input on this topic.