Sopularity is a simple tool with a three box interface. You enter your tweet as you wish to send it. Sopularity then looks at the tweet to suggest the best hashtags based on the content of it.
Sopularity suggests the most appropriate trending hashtags for your tweets.
This leads to a significant increase of the searchability and popularity of your tweets.
So what you seem to get is analytics based on the content comparing you to other tweets that seem close. You can choose to use them, change them and still add your own.
An interesting idea on how powerful hashtags are.
Sign up for the service was free and they also offer a Chrome extension. If you have trouble finding the right hashtags to have those that do not follow you find them, then this might be the tool for you.