Viraj,
I don't think you will have success with UHF,VHF or similar frequencies.The intensity of field strength decreases strongly from antenna towards the field and you have to count with nodes where field strength gets near to zero;signal reflection makes any effort vain.
In the shortwave range i know about some application with low power hf-oscillators that can be detected....but that means that you put antenna wires into the ground/floor...
Not all the frequencies may be used for such applications,be careful.
May be ultrasonic devices could work,but they make any dog crazy....
Blind people have many skills we 'illuminated'people do not have so well developed....try to search in that direction.
Edgar