Not sure exactly what you mean by this, but you can use Wordtracker to see what the competition for keywords are in different search engines. Also, you can use some available tools from seologs (i think this is the site) to check where you rank for certain keywords across different google data centers. hope this helps!
I use mcdar.net for google and some times i use this tool http://www.reladvance.com/metrix/find_metrics_form.php.
Tool to find out keyword positioning, wedding dress for example,for your url against the competitors url for this keyword.?
I think there's no accurate tool to check keyword positioning in Google Yahoo and MSN? I do it manually by checking the my target keyword search in these 3 SE. Manual checking of keyword positions is the most accurate....
Yes, there is no accurate tool currently for this.. not even in the Google Webmaster tools.. I would recommend to use the respective search page for this task