I have built this plugin AutoMeta for K2 to enable automatic generation of meta keywords and description for K2 items.

Its very easy to configure a template for keywords and desc on the level of a category or all categories, it this template you can use Item title, Category name, Tags or Extra Fields placeholders to be automatically substituted with the real value dynamically and on the fly, without any interaction webmasters.

I'm looking forward to read your impressions about it, and whether it can be developed more to meet your needs.