It is my opinion that most of the paranormal literature points to the fact that it is important to collect this data, but it just isn't stressed as to how important it is. Therefore, the beginning investigators often overlook this data and focus on more interesting areas. It is time to get back to the basics and find a nice and simple way to work this into our investigation practices.

The GE Wireless Digital Weather Station is a great place to start. This unit has the ability to measure ambient air temperature and relative humidity in up to 4 different locations. It is very simple to use and doesn't take a rocket scientist to interpret the readings. The system setup is simple being that it is compact and complete. Best of all, the unit is reasonably priced.

Unit Specifications
The Wireless Digital Weather Station boasts some decent range specifications for its price range.
Temperature Range (Base): 32°F to 122°F (0°C to 50°C)
Temperature Range (Remote): -58°F to 158°F (-50°C to 70°C)
Temperature ResolutionL 0.1°
Humidity Range: 20% to 95%
Humidity Resolution: 1%

I did a lot of searching on the Internet for the temperature and relative humidity tolerances, but was unable to find them at the time of publishing this article. However, I have done quite a bit of measurement comparisons with other more accurate equipment that I own. The temperature measurement accuracy was pretty impressive. The relative humidity accuracy did suffer slightly, but were close enough (within 7% in all the readings, which I was a bit surprised in a good way) for me to feel comfortable enough to recommend the unit.

Pros The unit offers great temperature accuracy and a workable humidity tolerance for its price. I spent $39.99 for mine. I admit that it unexpectedly exceeded my accuracy expectations.
The ability to measure temperature and relative humidity remotely. The unit also offers the ability to add a total of 3 remote sensors, which means that a total of 4 locations can be measured and monitored simultaneously.
The unit offers a date and time clock, which is useful as you don't need to glance down at your watch every time you take a reading. The moon phase is also included as well.
There is also a basic trend monitor to alert the user that the temperature or relative humidity is rising, falling or stable. Though there isn't access to the data that creates this trend, the fact that it informs the user of the direction of the trend is pretty nice.

Cons Most of the negative press this unit has gotten seems more to deal with the use of the remote sensors outside and when the remote unit was fairly cold. Because of this, I am fairly skeptical of the usefulness in this type of environment. I certainly wouldn't suggest using the base unit on an outside investigation regardless. The remote sensor seems to work fine if it isn't really, really cold.
I also don't like the fact that you can't turn off the system to save the battery. Though the specifications claim a whopping six months of battery life (2 AA batteries in both base unit and each sensor), it is a bit of a bummer that you can't turn off the base unit or the remote sensor.
The moon phase indicator cycles every 5 seconds. It is a bit annoying and I can't see any useful reason for doing this! File this under "what were they thinking".
There is no back lighting on the unit, so you will need a light source to look at the readings. This could be a hassle depending on how often you wish to take a reading.

Wishes I wish the relative humidity accuracy was a bit better. It is difficult to get a really good reading for relative humidity to begin with, but this unit certainly is reasonably accurate on its own.
I really wish this unit measured barometric air pressure. Other more expensive units do this and it is somewhat a bummer than they left this out, but this is probably what allowed GE to make this unit more reasonably priced.

Suggested Operating ProcedureObviously the base unit needs to go where your operations base is. This is the portion of the system that displays the readings from the sensor in the base unit and for each of the remote sensors. The remote sensors can be placed at each location that you would like to monitor (up to 3 remote locations). Let the units sit for about 20 to 30 minutes before you take your first readings to allow the readings to settle.

I would suggest taking a reading at 1 hour intervals and when something unexplained happens. At the end of the investigation take the minimum and maximum readings as well (the press of a button on the base unit will give you this data). This should cover you pretty well as far as environmental data collection.

One warning - I wouldn't substitute this system for a more accurate and faster response time digital thermometer that you can carry around with you. This system should be used in conjunction with a hand held temperature measurement device.

What I have heard I have heard some complaints about the maximum distance that the remote sensor can be away from the base unit. The GE literature claims that the distance can be up to 100 feet. In my tests, I got the remote sensor 100 feet away, through walls and near computer monitors and didn't have an issue. But I wouldn't feel right about recommending this item without making sure that I mentioned this fact. The reality is that this is a low wattage RF device and it should be obvious that natural factors can affect the signal. You will need to keep this in mind and may need to put up with some frustration in setting up the sensor network when you get out to the extremes of the signal coverage.

Conclusion Measuring basic location environmental data is essential for mapping out trends that could possibly point to a "best suited environment" for paranormal experiences. This type of data could also serve to validate or disprove other forms of evidence. It is just as critical to record and report this type of data along with your picture, video and EVP evidence. The bottom line is that this unit is a pretty good starting point for the beginning to mid-level investigator without the need to spend a lot of money.