Unfortunately, the previous answers take a poorly-worded Newegg product listing as an accurate description of the product, which is a shame. Look closely at the actual product photograph and see that it claims to be an "Electromagnetic radiation detector" which is an accurate description. It appears (from this alternative Amazon listing) to cover a frequency range from 50Hz up to 2GHz, which is of interest to domestic users with devices operating in the radio- and microwave spectrum.
The exposure safety limits of this part of the EMR spectrum are under intense debate because it is the part of the spectrum used by mobile phones, DECT, WiFi, Bluetooth, Zigbee (including 'smart' meters) as well as your domestic microwave oven. Without opening the 'conspiracy' can of worms, there are massive commercial interests which utilize this spectrum.
In Australia, exposure limits are regulated by ARPANSA. The "Radiation Protection Standard for Maximum Exposure Levels to Radiofrequency Fields - 3 kHz to 300 GHz (2002)" and supporting material can be downloaded here. Exposure is limited to less than 10,000mW/m2. Other countries have other limits - a good list is here. Note for interest that Russia and China limits are 100x less than the US.
The radiation from wireless devices is quantified as 'Specific Absorption Rates' in W/kg. The 1998 guidelines from ICNIRP (International Commission on Non-Ionizing Radiation Protection) state:
Exposure to more intense fields, producing SAR values in excess of 4
W/kg, can overwhelm the thermoregulatory capacity of the body and
produce harmful levels of tissue heating.
The ICNIRP guidelines form the basis for country-specific regulations, for instance the Australian ARPANSA "Radiation Protection Standard: Maximum Exposure Levels to Radiofrequency Fields – 3 kHz to 300 GHz" notes:
This Standard is based on the guidelines developed by the ICNIRP committee
You can look up, for example, the maximum SAR generated for different mobile devices - an iPhone 6 has a measured maximum SAR value of 1.18 (depending on the precise model) see here. Note also that the text instructs: "Carry iPhone at least 5mm away from your body to ensure exposure levels remain at or below the as-tested levels."
Other answers have pointed out that the radiation in this part of the spectrum is non-ionising, but they inaccurately conclude that it is harmless or inert. There are many scientific studies that show biological effects from radio- and/or microwave radiation well below current exposure limits. One of the most comprehensive reviews of the literature was performed by the BioInitiative Working Group, revised in 2012. Access that material here.
There is scientific research to the biological mechanisms for EMF exposure to cause biological effect. For example, this paper reviews 23 studies of the interaction of EMF radiation with the voltage-gated calcium channels (VGCCs).
The author of this paper says:
The paper goes on to consider how VGCC activation can produce two well-documented
responses to EMF exposure: stimulating of bone growth and the production of single
stranded DNA breaks in EMF-exposed cells.
In 2011 the World Health Organization classified cell phone radiation as “2b - possibly carcinogenic”.
Some people develop Electromagnetic Hypersensitivity, making them feel physical symptoms when exposed to electromagnetic fields. In Sweden, this can be officially recognised as a 'functional impairment' and treated accordingly. While the direct cause of electromagnetic sensitivity has not yet been established This paper from 2014 suggests myelin damage from EMF exposure may help explain it, saying:
Overall, evidence from in vivo and in vitro and epidemiological studies suggests an
association between RF-EMF exposure and either myelin deterioration or a direct impact
on neuronal conduction, which may account for many electrohypersensitivity symptoms.
The type of device demonstrated in this video can be very useful for those that wish to understand their environmental exposure to radio- and microwave EMR. These devices are not laboratory-grade but can be used as a useful tool. They can measure both power (mW/m2) or field strength (V/m). The video demonstrates that the high-frequency switching circuits used to drive compact fluorescent globes actually emits EMR at levels significantly higher than background. However, I can't tell what unit of measurement is being used, nor the frequency range being measured.
So, to the substance of the question asked:
- can the detector measure 'dangerous radiation'? The detector measures EMFs up to and including the microwave spectrum. Scientific evidence exists for thermal effects and non-thermal biological effects of microwave EMF radiation. Radiation exposure limits for this part of the spectrum are regulated. This device does not measure Standard Absorption Rate (SAR), therefore the device can only indicate the presence of EMF radiation and provide a relative measurement. It does not show the frequency of the radiation detected. It cannot be used to determine 'danger'.
- is the video showing 'dangerous' radiation? The video shows that the CFL globe is emitting radiation which is detected by the device. We cannot conclude that the radiation is dangerous.
- is the video showing that CFL globes are dangerous emitters of radiation? Given that radiation intensity falls as the inverses-square of distance, we can't see what the radiation levels are at 'normal' operating distances from the globe. We cannot conclude that the radiation from the globe is dangerous.
So, my personal take: I would think twice about putting that globe in my underpants all day long. However, I have held my own EMF detector (A Cornet ED65 'Electrosmog meter', range 100Mhz-8Ghz) next to spiral CFL and round CFL in my home and not detected any increase in reading. In my opinion there are many other domestic EMF sources that would be more concerning. I would be more concerned about the light spectral quality, flicker and mercury content of these lights.
Edit notes: thanks for the feedback on my response. I hope I have provided more adequate citation for the statements made in this answer.