Chatting with Deweyoxberg last night, he was interested in how I do my automated harvesters. They're nothing special, but they are scalable in both length and width, so can be used to create huge amounts of food in one go.
I don't have one on frontier currently, but this is how I build'em:
Create two lines of block, 8 long with a space between them. This will be the receiving channel.
Cap the far end and give it wings. Then, make a box around the wings and remove the two upright guide blocks. You should get a 5x1 channel with a hole in the centre.
Using dirt, create the bed that will be used for your grow-op. It'll be 5 wide, and 7 deep for the first section, then 5 by 6 for any sections further up. You want to do this as you'll have a bumper strip that you can walk on and the water will flow over the edge. This can be made as long as you really want. I'm showing 3 sections, but can go quite far.
Give each field a set of bumpers on either side as water guides. Thes should be raised up 1 block from the field. At the end of each section, box it off so the beds are raised one, and you establish your bumper strip.
When you have it as long as you want it, you'll want to create the water spreader at the end to flush the fully grown wheat to the collection trough.
Make a box something like this:
Then add baffles.
Stand under those holes and place upside down pistons like this, then fill in the holes. Fill the blocks behind the pistons with water, and check the flow. I had to add another row of stone blocks to get the flow on mine to settle out here.
Place a block over the water, and behind the pistons for your redstone.
Add the redstone like so...
Run it all the way down to wherever you want your toggle to be. I usually have mine at the front by the collection chute. Place repeaters (arrow facing towards the water source) as needed. Place a lever at the end and toggle the water flow off.
Once everything looks good there, then start on the irrigation. Make a 1 block high pipe on both sides for water to travel through, as I have here:
Be sure to block it off on the bottom too. (and light the place up while you're underneath. Creepers can make a mess of the thing.)
Block up the sides, leaving the space inside the pipe for the water to flow. Place your water source 2 blocks in from the rear of the high point. If done right, you'll see water at the end of your pipe. If you see that on both sides, you're done. Till the soil, plant it from the bottom up to avoid compacting the dirt, and flip the lever when you want to harvest.
You might notice that I moved the redstone onto the top of the pipe so I could place torches. Just be careful that you do this either on an empty field or have some way to ensure the pistons are down or you'll lose your crops.
The harvester in action: