I'm not asking about repairing my code or something I've just have a problem on where to or how to put methods in proper places in my application.
I wrote an application enhancing bluetooth chat - I made service for this bluetooth chat that runs in background. I will have more such services. Basically I want to be able to run methods across whole my application:

* send message via bluetooth chat and wait for answer,
* scan RFID tag with NFC,
* scan Barcode with camera,

etc.

Each of this I know how to do in 1 activity easily. Now I'm looking for a solution to put this in something like a global class that will allow me to call this methods across my whole application - so I don't have to initialize anything but just - doSomething() and it does it.
Where should I put such things:

* in custom activity class (all my other activities will use it)?
* in application?
* something else?

The same applies to handlers. Basically as to bluetooth chat you have to make handler to listen to received messages - where to put it as well.

I'm basically looking for propositions on how to solve this.