I am planning for a wireless controlled robot project. What is most effective wireless link item for controlling using two Arduino uno. Not only does this have to be the most effective, but it also has to have the lowest cost. I need this project to be cost friendly. Also, the transmitter and receiver must be two parts only and can't be like several parts like the xBee. I would say around maybe $15-$25 for two wireless parts would be reasonable in terms of cost friendliness.
I have researched that several different wireless transmitter and receiver signals can be easily disturbed by other surrounding signals (correct me if I am wrong).