I think the most useful technologies would be recordings and videos of masterful playing to give examples to follow. To have the final result of what good playing looks and sounds like.
As for bad habits, I don't believe they're such a fearsome thing. The way I look at it is a continual refinement. At first there may be obvious and fundamental problems to be fixed, and over time the work becomes more and more fine - so long as the learner is diligent about it. I figure a flawed beginner technique is a step ahead of nothing at all, so take it from wherever it is.
There are plenty of useful sites on the internet to pick up theory and ideas about music, interviews and inspiration... As for learning HOW to play, I find words can be hard to work with, easy to misunderstand. So far as self monitered technique is concerned I like to follow the principle of kinesthetic ease and careful listening. It's also occurred to me that being able to watch ourselves play at a distance can be good. There are some motions that we become comfortable with but are clearly not necessary when we see it in action.