I could talk about this subject all day, and, then, some. With 14 years "hands-on experience as a restoration contractor and 7 years as an adjuster, I will try and provide some key points to consider. This is a long response, but I think that you will find it helpful.
I always consider these three companies for moisture meters: Dri-Eaz (one of the largest manufacturers of drying equipment and restoration eductation) at www.Dri-Eaz.com, Tramex (one of the oldest moisture meter companies) at www.tramexltd.com, and Delmhorst (another long term manufacturer of moisture meters) at www.delmhorst.com.
1) Dri-Eaz. The Hydrosensor is a must have tool (cost from $140-$170). The difference between I and II is that one model is collapsable. This pin meter is used strictly for mapping the migration of water in carpet and pad. In recent years, Dri-Eaz has switched from using moisture meters designed by Tramex to now using the GE Protimeter. The top of the line model is the MMS Plus (approx. $1,100).
After determining how far the water has migrated with the Hydrosensor, I use 1" blue tape to map the carpet, and, then, photograph for documentation. I have owned the GE Protimeter MMS Plus and did not like the curved back of the meter. The curved back of the unit is for non-penetrating moisture readings. This package does have a lot of bells/whisltes, including software for transferring data.
The Wet Chek is a pin meter that some contractors give to adjusters. As with most pin meters, the meter only detects what the end of the pins touch. As such, you are not getting a true reading of the water damaged area. Since mold and liability issues have become a big issue in recent years, I would not reply on this meter.
"Remember, you get what you pay for."
2) Tramex. Their site has a multitude of meters. I am in the process of upgrading to the Moisture Encounter Plus ($385-$400). This is also another must have tool. This is considered a non-penatrating tool, which allows non-destructive testing, 1" penetration through materials, multiple readings of wood, drywall, carpet, vinyl, tile, wall coverings, and roof membranes and coatings. This meter also allows comparative readings for other types of materials. The "hold reading" feature is nice, plus the audio sound, when moisture is detected.
This is a great tool for quick spot checks for discovery of moisture migration. I test on wood floors, baseboards, drywall (start at the base and test to see how high the water wicks), cabinet/vanity toe kicks, side panels of cabinets, and on the lower shelf of cabinets/vanities. When testing cabinets/vanities, moisture readings will let you know that the particle board toe kick and support legs are wet. Once wet, particle board expands and loses its integrity. When moisture readings are found on the lower shelving of cabinets, this lets you know that a substantial amount of water may be under the cabinets. The readings are due to vapor readings of the water evaporating. Again, I use blue tape to map the wet areas and photograph.
The Professional Meter is a digital pin-meter ($310). For restoration contractors, this is another must have tool. With other pin extensions, this tool can get readings into hard to get places and other types of materials.
I also own the Tramex Concrete Moisture Encounter 4. This tool is in the $400 range and should be owned by both restoration contractors and every person that installs flooring of any type. This tool tests the vapor emission emitting from a concrete slab that has had water damage. This tool with various other types of readings should be used before any type of flooring is installed.
This is another established company like Tramex. These meters are pin meters. While the Navigator Pro is the top of the line meter, the BD-210, which I have owned, is a good all around meter. The BD-210 tests wood, gypsum, and several other types of materials. You can also purchase extensions. I, personally, think that this meter is more for restoration contractors.
I, as someone else stated, have never had an adjusting firm or carrier, require a moisture meter as part of your required tools. By the time that an adjuster arrives on site, emergency services should be well under way. The restoration contractor should have tested and documented with blue tape or the dot system and photographs.
Having worked with over 30+ carriers, I have found that most carriers do not mind that an adjuster carrriers some form of moisture meter. Yet, during my time in Florida with the hurricanes, I found that some carriers do not want you to bring moisture meters on site or show them in the photos. Some carriers do not want you to discover the extent of hidden water damage. They only want you to write a scope for what you can see. They feel that it is the contractor's responsibility to discover the full extent of damage. Because of my diversified background, I disagree. I guess it depends on your background.
Liability can be a problem, especially, if you have never taken a water damage class from the IICRC. There are many variables involved in discovering the extent of water damage without demolition.
A moisture meter, with the education of a water damage class from the IICRC (www.IICRC.org), can help you check the degree of damages before/after emergency services begin, and to prepare a more accurate scope of work for emergency services and repairs. Again, it may depend on the carrier.
At the least, I recommend the Dir-Eaz Hydrosensor II, the Tramex Moisture Encounter Plus, and, if you can afford it, the Tramex Professional Pin Meter (extensions available).
Again, this recommendation is based on my own experience. Please let me know if this helped or if you need further info.