How can I add a system service to Android?
You need to build a system application if you want it to be permanent..  Their is other ways to implement the service, like using init.d and some shell commands to be run at each boot .. 

However the easiest method would be to build a simple Auto Start application that starts the service.  

I found this answer on SO about building an Auto Start application that also starts a new service... 


  Answer on SO


It's fairly easy to build... Once you've built the application, try to install it in the system/app folder and see if everything works... You may have a locked system and can not modify the system apps... 

So you will need to use a command list that is run on each boot,... Init.d script should do that.