How far, small, and fast can meteors be detected?
Asteroids are usually tracked via optical telescopes set up for that purpose. If they get really close to Earth, they may be tracked via the space debris systems too. In some cases, extra observations are arranged for asteroids that look like they may get close to Earth.
Meteoroids are too small to be tracked at long range. There are some efforts underway to record the trails they leave when entering the atmosphere.