Your right forefinger.

Yeah....the one at the end of your arm :-)

Seriously, judging the soil moisture content by touch at rootball depth is by far the most accurate indicator. Generally, that only needs to be done for new plantings until they become established. After that, experience with your own garden, its soil condition and the weather will be the best judge of whether watering/irrigating is required or not.

Thirded. Mechanical meters are notoriously inaccurate. Learning to judge how damp your plants are is the best way to do it.

Yeah, it's kind of tough at first, but you'll pick it up pretty fast!

Before you ask, there's no good pH meter, either, and no good pH test even in vials that matters much anyway. Even if they were to give a perfect answer (mostly they don't), it's not significant information. It tells you nothing about what's causing the pH or how to fix it if it's off--should you add calcium, magnesium, or potassium? ... Exactly, they say nothing about it.

So basically, just skip meters and pH tests and save the money. :-)

well .. of course.. if your left handed.. your left one is just as handy ...

understanding your soil .. how it drains.. soil type.. etc.. is all information you get by playing in the soil .. and will never be learned.. by a gizmo ...

and after you are done playing in the soil... you will be covered in dirt.. and usually track it in the house ... and you are going to get dirty walking around with the gizmo anyway ... so why bother ....

btw.. money saved is usually used to buy more plants ... or for replacing the ones you killed.. when your finger failed ...

ken