the ca3130 only works to 10 mhz, cell phones are much higher in frequency. here is a detector that will work.
http://www.techlib.com/electronics/feddetector.htm
even on the newer digital phones.

Your link removes the speed problem with the opamp and puts the responsibility on the Shottky diode.
Their MAX478 is only good to 60,000 GBW.

 

there are very few op amps that work to 2,500 mhz. an mmic or so might get the rf gain up to enough.

 

The opamp is not amplifying 2.4GHz, only slowly varying DC. The RF is envelope-detected (rectified) by the protection diode at the input of the opamp. The detected envelope is what comes out of the opamp.

 

The CA3130 works just fine in this circuit, but is hard to come by these days. A LM6482 is a more modern op-amp that will work.
It's not needed to go to GHz, as it's the pulse bursts that sets it off (like phones sometimes interferes with badly screened amplifiers etc. (It's hard to provide good screening of the up to 2W bursts with brutal flanks).

It's a rather old circuit (which the use of the CA3130 should reveal) and the crucial part around the op-amp was posted - in Elektor in the late eighties IIRC.

The cap should have long leads and should be trimmed while testing.

If my mind doesn't play tricks on me, I think a circuit closer to the original one is on Red's Circuits.

Sounds like school work to me, so I'd like to see Parul77 do a little of her own foot work, before we just hand it all over