Your DX only reports battery readings in 10% increments. Any application that you may find reads from the DX, so it can't actually give you a better reading than what it's being given. You won't be able to find a battery widget or monitoring application that gives you a more detailed reading and actually have it be accurate at the same time. If you find one that gives you more, "accurate," readings, it will only be working through guesses and assumptions.
Unless someone has found a way of reading the battery in a different fashion, without going through the usual channels, there isn't a way to actually do this. I want more accurate readings too, but last time I checked, it isn't technically possible for the DX right now.