My setup cost me only $50. Hawking HWREN 1 - $27 (used), 12V 3000mah DC battery pack - $15, and 7dbi Alfa Directional Antenna - $8.
You just set up the HWREN 1 to repeat the signal from the camera, rename the repeater something like "FC40_Extender", connect your phone/tablet to it, and open the app! As I have found out though, iPhone 4/4s may or may not play well with these setups (my iPhone 4 won't work but my old 3GS will).