As kcwcc said the meter side is fairly trivial, you just need some opamps to condition the signal and a simple meter to display it, either an analogue voltmeter or an LED one - try a 7107 from Microchip.
http://www.electronics-lab.com/projects/test/014/index.htmlThat one above is very easy to make, the main 7107 chip is free on Microchip sample program.
Its the sensors that are going to be tricky, the pH one anyway.
http://www.66pacific.com/ph/simplest_ph.aspxHere is a simple one, you just need the probe. They use a conductor in a glass rod, not so easy to make.
http://en.wikipedia.org/wiki/Glass_electrodeEC tho is easier. You are basicly measuring the resistance of the solution, but you must use AC or otherwise you will get electroplating or electrolysis caused by passing DC through a conductive solution.
If you set up opamps to compare the amptitude of the AC signal before going through the solution and afterwards the difference should be the EC. You will need a solution of known EC to calibrate it against.
Easiest way is find a friend on the net or elsewhere, get him to add say 1 gram of salt to one liter of distilled water and measure. Then add another gram, measure. Then another etc. Then you have a calibration curve to work against.
Good luck.