One of the most common (and cheapest) ways to deal with early wakings is to teach your child how to tell time and let them know that they cannot come out of their bed (or bedroom, if you prefer) until X time. Most kids won't be able to completely tell time yet, but if you let them know that they can't get out of bed until the first number says, say 7, then even a pretty young child should be able to figure this out. Another way is to attach a timer to a night light.

If you have a very young child that can't quite figure out a clock or you simply want something else that's a little more fun for them and even educational, there are a few options that you'll find listed below. Very good is the teach me time clock and the kid sleep clock (cheapest clock and easy for really young children to understand). If you want something fancier, keep reading and you'll find something for your child.

The great thing about most of these clocks/lights is that they can be a cue for bedtime as well as wakeup time and they help some children reduce night wakings. And many of them can be set for other times, like naps, so you don't have to reprogram things each day. Some things to consider: Is it battery or plug operated? Do you want a night light? Can the night light turn off if desired? Do you want a digital and/or analog clock?

OK to Wake!

• Green light turns on when it is time to get up
• You can use it as a yellow night light during sleep times or turn the light off during sleep times
• Separate nap timer
• Battery operated only
• Alarm clock with snooze for older kids
• You can press the toes to make funny facial expressions
• Face on the clock isn't backlit so hard to see at night (you can push the toe to light it up)
• Concealed control panel so kids can't change the settings
• Interchangeable pink and green bezels. You can buy it here

Teach Me Time! Talking Alarm Clock and Nightlight

• Night light that turns green when it is ok to wake. You can also turn the night light completely off by setting it to the same time the ok to wake light turns on. You can figure out how to turn off the feet lights by looking at the first few amazon reviews.
• Helps children learn to tell time with a light up face and with an interactive time game
• Alarm clock and snooze
• Adjustable volume and brightness
• Battery and plug operated
• Concealed control panel so kids can't easily change the settings
• Comes with pink, blue and yellow interchangeable bezels. You can buy it here.

Kid's Sleep Classic

• Night light
• Wake up indicator - when the sleeping animal is lit, time to stay in bed, when the awake animal is lit, it is time to get up
• Alarm clock and nap setting.
• Comes in pink, blue and green (smaller)
• Item seems somewhat low quality and difficult to program. Buttons are easy for a child to push.
• Plugs in
• 3 brightness levels. You can buy it here.

My Tot Clock

• Plugs in and can be battery operated
• Clock turns yellow when it is time to wake up. Is blue during sleep times
• 5 levels of illumination, including off
• Also has a green and red light that you can set for other things like nap time or activity time
• Alarm option
• Music and white noise option
• Story option
• Changeable faceplates. You can buy it here.

Gro-Clock

• Sold mainly in the UK and Europe but it looks like you can buy it in Canada here and in the USA here.
• A yellow sun comes up when it is time to get up. At night there are blue stars that countdown until morning (you can turn these off at night)
• Digital clock display (optional)
• Second time setting that can be used for naps or weekends ( suggest that you keep weekends the same as weekdays but obviously this doesn't happen for many families)
• Comes with a bedtime story book to encourage kids to stay in bed until morning
• Plugs in. You can buy it here from the UK.

Stoplight Sleep Enhancing Clock

• When the red light is on (no way to turn it off), it is time to sleep. When it is green (goes on for an hour), time to get up
• Digital clock
• Alarm
• You can also buy a boy in a car, a train, and owls. You can buy it here.

OK To Wake! Owl With Night-Light and Music

• Face glows yellow at night(for up to 2 hours) and green when it is ok to wake. Green light only stays lit for a short time then the child has to push a (supposedly difficult to push) button to see if it is time to get up.
• Music with the push of the tummy (difficult to push though)
• Nap timer
• Adjustable volume, brightness and auto-off duration
• Battery operated. You can buy it here.

source: http://www.mybabysleepguide.com/2012/05/ok-to-wake-clocks-and-lights-for-early.html