Permanent daemon for quering a web resource

I have a rails 3 application and looked around in the internet for daemons but didnt found the right for me..

I want a daemon which fetches data permanently (exchange courses) from a web resource and saves it to the database..

like:

while true  Model.update_attribte(:course, http::get.new("asdasd").response)end

I've only seen cron like jobs, but they only run after a specific time... I want it permanently, depending on how long it takes to end the query...

Do you understand what i mean?