I frequently use a URL field in my metaboxes. I put in “http://” as the default text to remind clients to include that. Then when I store the value, I check and if it is still just “http://”, I just treat it as a null string. Is that something that is supported by Piklist?
Also I have code that checks for valid email addresses … I didn’t see an email field either … that’s another field type that would be very useful.