This Wireling lets you measure the intensity of magnetic fields via the A1454 Linear Hall Effect Sensor or the TCS40DLR Discrete Hall Switch. This particular version of the A1454 is intended to be used with ferrite type magnets.
You can read about the differences in common magnets here.
Allegro A1454 Hall Sensor Specs (Analog)
Toshiba TCS40 Hall Switch Specs (Digital)
TinyDuino Power Requirements