Buying meters for DWC, are they good for soil?

I need to buy ph/ppm meters for my little DWC setup, but I'm wondering if I decide to start a soil grow will I be able to use the same meters? Do I have to buy one of those kind that has prongs to stick in the dirt? I'm thinking of picking up this deal here..
http://www.pchydro.com/tools-digital-testers-c-31_115/digital-ph-ppm-meter-combo-deal-p-4157
Is that a good deal? Can you recommend a cheaper buy? I know if I get these things I need all the solutions for them. I figured if I can get them all in one package it would be better.

edit: I've got ph drops, been battling my ph down from green to yellow every day. Should I just start buying RO water from the grocery store? They have a machine that sells it for $0.49 a gallon and its just a block away.

yes any grower should have them if they want to have a happy plant helps in many ways in all seriousness cheap is not always a good idea get a good brand will always come in handy

Yes, I know I need them. What I don't know is if I can use THESE to check a soil grow. Also, would RO water help my daily battle of the ph going way up?

Yea, I think you are better off getting hydro meters, the soil meter is only $10 and sucks anyway.
I use hydro meters to pH my water before I water/feed girls in soil. That's what you need.

The way to test the pH in your soil is with run off. Get your water ready, pH to say 6.5 and water real good.
when it starts to stop dripping out of the pot take a sample of the water and pH that. That's the closest you are going to get.

The other thing is a ppm meter, test your tap ppm and pH.
mine is 330ppm and pH 7.0 I use a sediment filter with a carbon filter combined, called a smallboy. google it, anyway that brings me down to 250ppm and thats acceptable. the carbon filter removes the chloramines so I can use it right away, you can let it sit with an air stone for a day instead but anyway check your tap, you could be good and dont need r/o water. Tap will make your pH rise as your plant uses nutes though so keep an eye on it.