Most digital cameras and digital SLRs come with a small LCD display which you can use to see what you are shooting. If you need a larger display to keep up with things more easily, you are going to have to pick up one of these external monitors:
DLC Swivi External Swivel 5.6″ diagonal LCD Monitor: this is a 5.6 inch external LCD screen for your DSLR. It has an HDMI port and Live-View function. It uses 6x AAA batteries.
LILLIPUT 5DII-H DSLR Camera: has a 7 inch LCD display with 250cd/m2 brightness and 160 degree viewing angle.
ProAm 7″ On-Camera LCD Video Monitor Kit: lets you view your live footage as it is being recorded. This 7 inch monitor attaches to your video camera using the accessory shoe adapter.
COOLLCD HD2 7-Inch HDMI Monitor: a 7 inch HDMI monitor for your DSLR camera. It has minimal blue-screen delay. It is compatible with Canon 5D mark II, Canon 7D, and other devices with HDMI or mini-HDMI.
These external monitors are large enough for most pros. They are easy to attach to your camera too. They won’t be cheap though.