Have a look at this video, and don't forget to turn the sound on, before or after reading on. The video is very amateur but I am learning.

http://www.youtube.com/watch?v=eJB6QMmmTe9

I have been meaning to share this idea since I retired 3 years ago and discovered forums. I have never seen such a device mentioned, though for all I know everyone has one. It has been a godsend to me over the last 30 years. The idea is of course not new; there are electric drum processors for colour, and the Paterson orbital motor driven processors; and before that there were rotating and tilting devices to mix blood samples and stop them coagulating in my previous life as a doctor.
One day in the early eighties I spotted in a surplus store catalogue an advert for geared electric motors, 30 revolutions per minute. A little experimentation with my developing trays suggested this was an OK if not ideal speed for rocking my trays. Keeping it cheap and simple, as I was not sure it would work, I fabricated the devices you see in the video (apologies, video editing not on my CV yet). Melamine covered chipboard held together by screw blocks. A crank attached to the motor spindle, and a 45 rpm record offset by the crank. A little bit of grease where the record runs in the groove of the plastic railing - I thought it would cut through but it never has. The motor runs on 110 volts, hence the transfromer, as UK voltage is 230 volts. A bonus for me is that the box lifts the dishes to chest level; no stooping to see what is going on in the dish.
I do not use a stop bath, and have found 1 minute in dev and 1 in fix at 20 C quite enough for RC which is all I use routinely, so the Isgus mechanical timer set to its 60 second maximum is perfect; if I want longer I wind it up again.
I do a lot of run -of-the-mill photography, so printing a 36 frame roll of 35 mm is regular fare, and made much easier by exposing six 5x7 inch sheets, and then developing and fixing them together in 12 x 10 dishes ;if the agitation is being done for you, this leaves hands free to make sure the prints don't bunch and stick together. You can also sip your coffee, take the neg strip out of the enalrger, change the record, whatever. In the video you see me in daylight placing six I made earlier in water; this is purely for illustration as I thought it would make clearer how the sheets slide over one another. For big enlargements in a 20 x 16 dish I normally process one sheet at a time and still use only 2 litres of dev or fix, and help things along with a bit of side to side rocking by hand as well as the motorised back to front rocking. Saves on chemicals and easier to pour out afterwards.
Only problem for you is finding a powerful geared or stepped motor giving 30 revs per minute; don't know where I am going to find them when these pack up.
Having said that I have been meaning to share this idea, I did in fact send a video to Nova Darkrooms about 15 years ago; the gist of the reply was that I was 20 years too late!