Gigahertz most popular RF detector the HF35c is highly accurate, directional (as much as anything can be in this multi-source Electrosmog world) and robust.  Considering its technical capability is it very reasonably priced too.
Ideal for shielding projects when mitigating cell tower radiation, smart meter or DECT cordless phone emissions, as the accurate directional capability allows you to adjust your shielding plan accordingly, it doesn’t though read high band Wi-Fi.  If you’re new to this scene, I’d go for this monitor for your newly discovered microwave radiation shielding guidance and supplement it with the acousticom which whilst none directional will accurately pick up anything high bandwidth that the HF35c misses.  If you can only afford one monitor buy the Acoustimeter this whilst none directional comes with LED readings which will help guide shielding projects and it will cover the high band Wi-Fi emission.