Pendulums can be used to help guide your everyday life and are simple to use. You can ask the pendulum yes or no questions and it should swing forward and back for yes and side to side for a no. Now you may want to buy a pendulum they usually look more nicer. Pendulums are also used to check if fruit is ripe but you don't have to.
I always use the pendulum and think they are amazing to use and would recommend using one. Bear in mind there is a load more things you can do with a pendulum I'm just stating the most common ^i^
One of the uses for a pendulum is dowsing. Personally I use two metal rods. But I know others who use a pendulum. And, just like dowsing, it is the energy of the person dowsing together with the energy of the Earth, that makes it work. With the two rods I can find water, and unused drains very easily. To find various metals needs the rods to be in contact with the metal you are seeking. Pendulums have been used for thousands of years to find directions, and also to find the sex of the unborn baby. They can show if an egg is fertilised. And it is amazing what you can find holding it over a map!
You can look at pendulums in two ways really. It can many times depends on your use of them though both fields use the subconscious energy. Some have used them as a tool of scrying (focusing understanding from the subconscious through an object or finding "inner wisdom") , or dowsing (finding information of the physical world through using and focusing earth energies in vibration to your own). If used in scrying, the pendulum is like any other object you use in scrying, it focuses your energy of what you desire or seek, allowing the vibrations your subconscious to physically shows a response through moving the pendulum via your own bodies vibrations). In other words, If you understand what scrying is, you understand what a pendulum actually does. It carried and physically shows your bodies vibrations through moving the pendulum. The weighted object on a string is actually for a reason. In order for your vibrations to show, their must be a medium light enough to be moved from your bodies even smallest vibrations. A string or chain is a straight (due to the weight keeping it so on the end) and light material. The weight at the end is able to keep the string/chain from simply shaking but rather moving in large enough movements to be more direct and obvious. It's also important to understand that your subconscious carries vibrations that many of us aren't even aware of. Your subconscious is constantly taking in information and remembers it from not only your experiences but from everything around and in ether. That is why scrying is such a useful tool and why pendulums have been such a long respected medium. The mediums use goes all the way back to the ancient Egyptians and Chinese or further back (not necessarily in scrying but rather dowsing), so you know the tool and it's form are well respected for a reason.
Now dowsing... As stated above, dowsing is focusing earth's energy such as ley lines, rocks, plants to seek/find things such as water or direction or even lost objects. Some do believe at the same time that the information still comes from the person's subconscious instead of the earth. Others believe both are the case but it's really your decision of what you think is correct cus either way the pendulum will still work. If you have any questions about them, email me.
Also, a good book for beginners I have used and learned about through others is "The Art of the Pendulum" by Cassandra Eason. It's direct and simple but enough information to fully understand without getting too far into detail.
Also, I can't imagine how in the world they can have any effect of your auric field as that would be saying that everything you touch would do the same. You can't "open" your field but rather extend it a bit which still will have no harm. If you know how to protect yourself with shielding/ground/center your in no harm even if "opening" your field were possible.