Upvote / mark as useful ?

Hi,

First thank you for this amazing plugin, it is really customizable.

Well now I would like to integrate an upvoting system in a similar fashion as in amazon, and then order the reviews by most useful.

Ex:
This is my awesome review for that product
[Mark as useful button]

This functionnality would then increment a counter, maybe from a custom field.

What would be the best way to achieve that ?

Thank you