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Just take a screen shot (by holding home button + power button) and then set it as the wallpaper in the settings.
 
That wouldn't be nearly as nice as large, clear text like sticky notes or something.
 
remindme does just that.

Also VoCal (Voice Reminder) may be a replacement for both things and remind me as it is very extremely fast and simple to use with no typing.
 
Another thing you could do (which I do occasionally) is to make a list in the notes app and then take a screenshot of that.
 
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