sensitive hall effect sensor

Can anyone give me a tip on a very sensitive hall effect sensor.
My requirements are "small, sensitive". And not sensitive in the way a reed switch is.

I'm about to detect small magnets through a glass window, and there is no rotation involved,
so it's merely there or not there, that counts.

A linear hall effect would be very sensitive.

See allegro microsystems,

Also, you could just use one of their hall effect switches if the magnetic flux density is strong enough.