I need a launch script which has access to "db" and other web2py modules. This script must be running constantly. I know that Web2py has launch parameters from which you can run python files in the web2py enviroment, but i don't know how that works. Can this parameter solve my problem and if so, how do I go about it? Thanks!
Look at section 4.17.1 of the web2py manual (or Google "web2py cron").
You can run a script on startup of web2py by registering it in the crontab file as:
"@reboot web2py *scripts/myscript.py"
web2py should be the username that it will run as, which should be the same as what web2py runs as. In my setup I have a user named 'web2py' to run the app.
The asterix before scripts/myscript.py indicates that you want to run the script in the web2py environment. 
Keep in mind that you run the risk of locking issues if your script is trying to use the database at the same time as the normal web2py process.
Web2py launch script