What are these eyeball statues everywhere?

Throughout the game, there are small statues with eyeballs on them. If you inspect it, Navi says something about a fairy being inside. If you whack it with your sword, it shows you the current time.

Is there something else these are useful for?

These things are called Gossip Stones. Aside from telling you the time when you sword them, they have a few behaviours:

• They act like rubber if hit by Din's Fire or the Megaton Hammer.
• They rocket into the sky and explode if bombed.
• They release a Fairy if Zelda's Lullaby, the Sun's Song, or the Song of Storms is played nearby.
• They reveal secret information (some useful, some useless) if talked to with the Mask of Truth on.