Here's a great metronome with extra features and low price!
It has a true "wood block" click. A440 tuning tone. 2/4, 3/4 or 4/4 time signatures, accented beats, headphone jack, and comes with battery.

Features:

• True Òwood block" click
• A440 tuning tone
• 2/4, 3/4 or 4/4 time signatures, accented beats
• Headphone jack
• Battery included