To get the Unlockables under the extras menu you must acquire the designated amount of Sly Masks hidden throughout the game.

Unlockable	How to unlock
Camo Paraglider	Collect 10 Sly Masks.
Cole's Amp	Collect all 60 Sly Masks.
Monkey Paraglider	Collect 5 Sly Masks.
Ratchet's Wrench	Collect 50 Sly Masks.
Ultimate Bentley	Collect 20 Sly Masks.
Ultimate Carmelita	Collect 40 Sly Masks.
Ultimate Murray	Collect 30 Sly Masks.
Ultimate Sly	Collect 15 Sly Masks.