Capabilities of a Hall-Effect sensor

[Michael Hill]

I am wondering if a Hall-Effect sensor could be use to sense how close a material is to it (using it much like a proximity probe). I'm talking about a range from 0-30 mils. The material being used is close to Inconel. Price is not an issue, so if you can find one, even if it's a couple thousand, please tell me. The only reason I'm asking here is because I know there are quite a few applications in robotics (such as gear tooth counting).