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RF Probe
Didn't really think that this would get published, but it did. December 2004 issue of Electronics World

A nifty little circuit for displaying RF (Currently set for the FM band: 88MHz-108MHz) signals on a low frequency oscilloscope. As there is no filtering at the input, the circuit will pick up both the main signals and the image frequencies. (If you don't know what this means, find out how a double balanced mixer works, and then look at the circuit for a receiver, just before the mixer stage. This is where some sort of tuning is present, to cut out the image band). Its assumed that you know roughly where the signals are supposed to be. The 100K pot is used to calibrate the unit with a known level signal, assuming that you have temporary access to a high frequency scope. L1 is 6 turns wound on a quarter inch former.

This is the artwork using Protel's DOS autotrax package, which can be downloaded from a number of places. Just put autotrax into the search engine, and you should come up with a number of hits.

Download Autotrax Artwork.

Below is a picture of the actual unit; used to measure the output on a number of FM transmitters.

If you want to save yourself the trouble of making pcb's, then the unpopulated pcb is available for £5 per unit.
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The 30pF cap of the resonant section can be replaced with some sort of varicap tuning, as detailed in the 602 datasheet, for more accurate readings.

As an aside, the RF power detection circuit in some mobile phones has a simple diode detector, with the input of the diode being switched to just-on by a forward biased diode from a dropper resistor. This is possibly going to have a wider bandwidth than the circuit, on this page.