Above proposed budget RF meters will do the job. Both can transmit over a wide frequency range. A maybe important difference is that WinNWT4 have a non frequency selective power meter as detector.
If however actual need is just to transmit a WiFi-signal and be able to detect a level can any WiFi-dongle be used to receive/transmit signals as well as most WiFi-routers can report actual received signal level, RSSI, directly in its software.
Nice spectrum diagrams software to be used with any dongle and a PC or cellphone:
http://www.metageek.com/products/inssider/
If the need is for something very portable, very budget and WiFi only, can two ESP8266 do the job Connect a small antenna loop to each unit and read/store RSSI.
"radio tomography" is for me something rather complex to measure if it includes measurements deep inside body tissues and then measuring of transmission loss between two antennas.
As long as possible do I prefer to do theoretical calculations, it is a lot less messy. It exist free body models as well as detailed tables such as this sait:
http://niremf.ifac.cnr.it/tissprop/
I do also use these tables of tissue dielectric properties to make my own body equivalents, basically mixing water, sugar and adding small amount of salt and a tiny bit of sulfur to stop fermentation.
Transmission losses inside human body is rather high at 2.4GHz which can make measurements more complicated as error sources such as reflecting RF along outside of cable braid causes isolation problems.
These things are easier to handle at lower frequencies such as 433MHz and at these frequencies are losses lower and a lot of cheaper tools can be used to do measurements.
A such example is nanoVNA
http://www.aliexpress.com/item/4000438307006.html
It can measure both reactiv and resistivity loss which in some cases are of big value, if not else, to be able to characterize antenna properties impact on measured result.