Encourage people to vote in polls - randomly pick a winning voter

[Spinball]

Hi folks,
we regularly run polls to get information about our members. This can be very very useful to present to potential advertisers.
As a way to encourage people to vote in a poll, I was thinking that it would be useful to do 2 things.
a) at the moment the poll can be set to close automatically after a certain amount of time. It would be useful to automatically close the poll after a certain number of votes.
b) when the poll is closed, it would be very useful if the registration name of one person who has voted could be picked at random and emailed to admin (or maybe a selectable user name). The winner would be the recipient of some kind of prize which the site could send out.
An option to automatically PM them (from the same person who got the mail) to notify them that they are the winner and request that they reply with their postal address would be useful.
Since polls are so useful, it's definitely worth motivating people by offering a prize to one randomly picked voter.
Thanks for reading.