Can You Make The GND High Or Low?

I am trying to automate my iPod touch 4th gen,i am also using an app where you watch videos to get points to redeem for paypal. I found that if you place a piece of folded copper foil connected to the negative battery terminal of a battery it is as if your finger is were the foil is (this is a simple capacitive stylus). Now i want to automate this so i can control when there is a contact, is there any way to regulate the flow of the GND of an arduino without the use of a transistor? i don't want to use a transistor since i would like to make this as simple as possible and using transisitors may be cheap and easy but i would rather it be super simple. Any input on better ways to make a contact with the screen making it so you can turn the ground low or high would be greatly appreciated, thank you.

The GND of an external device can be connected to any Arduino output pin. This pin can be between 0V and 5V higher voltage than the Arduino GND. Put it another way, the Arduino's GND can be 0V to 5V lower voltage than whatever is connected to the output pin.

I suspect that this goal is not possible without an external transistor.

Nikolas_Maples:
I found that if you place a piece of folded copper foil connected to the negative battery terminal of a battery it is as if your finger is were the foil is (this is a simple capacitive stylus).

What is the positive terminal of the battery connected to ?

What sort of battery are you using ?

...R

any way to regulate the flow of the GND of an arduino without the use of a transistor

You probably know this by now, the current you can sink through an Arduino pin is max 40mA.

One thing to try is to connect the ground of the iPod to the GND of the Arduino. Then you can run a wire from an Arduio pin to foil on the screen. To trigger the touch, switch that pin from pinMode(pin, INPUT) to pinMode(pin, OUTPUT). This should switch the wire from open-circuit (INPUT) to grounded (OUTPUT).