tattler

noun3

1. •
   One who tattles (notifies authorities of illicit behavior) or is inclined to do so; a tattletale.

   • My sister is a big tattler; she always tells Mommy when I hit her!
2. •
   Either of two similar bird species in the shorebird genus Heteroscelus (Tringa in some taxonomies).
3. •
   A device fitted to a vehicle to measure mileage etc.

   • A few truck drivers griped drowsily about the tattlers in their cabs which graphed the mileage per hour per day. — 1960