I found a wonderful wordpress plugin Comment Info Detector

This plugin can detect information such as country name, web browser and operating system from your commenters and then displays them on your comment section or anywhere you like.

Features:

• Detects and shows commenter’s country flag, web browser and operating system automatically
• Supports many web browsers and operating systems: major desktop browsers, antiquated browsers, blogging software (for trackbacks and pingbacks), text based browsers, various PDAs and cell phones.
• Uses a binay file for IP to country resolution and supports database sources from Webhosting.info – Software77.net
• The returned string can be configed as a template to suite your theme

Here is screen shoot of plugin