Using chip antennas over a 50 foot distance
I think you're a bit confused with regard to the terminology here.

You link to an XBee, which is a microprocessor, connected to a RF tranciever, which has an antenna on it. You do realize you need the microprocessor and RF tranceiver, correct?

Even something as simple as sending a simple on-off signal is fairly involved. You need some sort of transmitter and receiver in addition to the antenna, you know!
Realistically, RF (radio frequency) design is hard. From your question, I think it may be a bit over your head.

There are certainly highly inexpensive RF transmitter-receiver pairs (take this tx/rx pair from Seeed studio - $4.90!). However, this will not do anything without an associated microcontroller. If you pair it with something like an Arduino, you could likely make it do what you want. However, that would involve a fair bit of work.

Realistically, assuming you just want to turn something on and off, a pre-built transmitter and receiver pair may be more along the lines of what you want.