I may be a bit late, but I just saw this thread. We have an 'Ok to wake' clock from Aldi. It's a similar concept to the others, but instead of sun coming up, a soft green light comes on when it's time to get up. So we have it set for 6.45, and DS knows it's ok to get up when his 'clock goes green'. The light is soft enough not to wake him if he still needs to sleep, while at the same time being an easy cue for a toddler to grasp. Works well for us!