How to create something that I turn on and off via a remote signal?

I want to tackle a small project, but don't know how:

The objective is to put something between a wall socket and say for example a tv's electricity plug. That is, the plug would connect to this object, and the object would connect to the wall socket.

The purpose of this object would be to allow and block the electricity to my tv whenever I so desire.
-What hardware do i need that can block or allow this current to flow. I'm assuming I would need a computer chip in order to have this be done via an external signal (which brings me to the second part of my inquire)

-If I wanted this 'object' to switch between on and off based on what I tell it via a remote control [or ultimately an iphone], what hardware and or software do i need to implement in order for my project to be able to receive and interpret a signal sent to it?

Powering on/off a 120V appliance is best left to something purchased. You can use a powerswitch tail for that:
http://www.adafruit.com/products/268

Now, what to use to switch it. An arduino or any other microcontroller would be perfect. Sparkfun used to have a nice kit, but it looks like it's retired. They may have another one soon.
https://www.sparkfun.com/products/10783

One way to do this would be to get a raspberry pi, and plug the pi into a network. Then via the iphone, you can control it on a web page interface. The pi is pretty cheap, but you'd need to have power supplies and other accessories. There's lots of tutorials for it. Get a kit to wire up the GPIO pins to the powertail and you're pretty good.

That said: propellers, arduinos, and lots of other kits would be able to interface.

EDIT: If you know nothing about a raspberry pi, maybe take a look at the adafruit tutorials for it. You can see what you might need to do to put it on a network and use the GPIO pins.
http://learn.adafruit.com/adafruit-raspberry-pi-lesson-1-preparing-and-sd-card-for-your-raspberry-pi

They just make remote controlled on/off switches for 120v apliances. I bought one at Ace hardware for my yard lights.