In support of medical applications such as the camera-pill which replaces painful gastrointestinal diagnosis with tubing and provides excellent results.
As cameras get better and need to transmit more data, standard radiofrequency channels would require large batteries to power the transmission. Instead, a wireless communication protocol using the human body as a transmission channel can be applied.
Note that the camera-pill or ingestible wireless capsule endoscopy (WCE) is the only painless, and effective diagnostic technology for inspecting the entire gastrointestinal (GI) tract for various diseases (ref).
Non medical applications are also cited in the article below: wristwatch could transmit a very small electric pulse that travels on the skin (it has been calibrated for the resistance of the skin – e.g. no need to reach underlying muscle layers). Data from a business card have been coded on this electric pulse. If two businessmen with the same wristwatch make skin contact via a handshake, electric pulses will travel on their skin and the information of their business cards could be exchanged on their wristwatches.
Some references follow
"Forget Bluetooth! Transmitting magnetic fields through the human body can connect smart devices... and saves battery power"
"Human-body near-field communication technology - New body-area network that uses the human body as a communication path"
"Human Body as Antenna and Its Effect on Human Body Communications"
Behailu Kibret* , Assefa K. Teshome, and Daniel T. H. Lai
Progress In Electromagnetics Research, Vol. 148, 193–207, 2014
"Human body communication (HBC) is a promising wireless technology that uses the human body as part of the communication channel. HBC operates in the near-field of the high frequency (HF) band and in the lower frequencies of the very high frequency (VHF) band, where the electromagnetic field has the tendency to be confined inside the human body."
"The human body acts as a waveguide in the frequency range of hundreds of kHz to dozens of MHz, which is considered suitable for HBC operation. More specifically, IEEE 802.15.6 defines 21 MHz as center frequency for HBC. HBC uses near-field coupling that leads to low radiation to free space; as a result, it promises a secured low data rate communication. Due to the low propagation loss, it also promises higher communication performance compared to other body area communication techniques, such as ultra wideband (UWB) ."
Magnetic fields provide a new way to communicate wirelessly
Interesting figures for calibrating resistance of different tissues (skin, fat, muscle etc)
Human-body near-field communication technology
"Broadly speaking, there are two approaches to using the human body as the transmission path for communication: the electric-field type and the electric-current type. The electric-field approach was first verified by Zimmerman of MIT  and then improved in terms of speed through work by NTT using optical sensors in the receiver to achieve a transfer rate of 10 Mbit/s . The electric-current approach, on the other hand, is used in body fat measurement, which uses a very weak current flow, and there have also been reports of application to retail scales for weighing products like meat ."
"IEEE releases new standard for body area network"
"After five years of work, the IEEE announced a new standard, IEEE 802.15.6, for wireless communications supporting ultra-low power devices operating in or around the human body."
"7 things you should know about Body Area Networks (BANs)"
Initial applications of BANs are expected to appear primarily in the healthcare domain, especially for continuous monitoring and logging vital parameters of patients suffering from chronic diseases such as diabetes, asthma and heart attacks.
· A BAN network in place on a patient can alert the hospital, even before they have a heart attack, through measuring changes in their vital signs.
· A BAN network on a diabetic patient could auto inject insulin through a pump, as soon as their insulin level declines.
A typical BAN or BSN requires vital sign monitoring sensors, motion detectors (through accelerometers) to help identify the location of the monitored individual and some form of communication, to transmit vital sign and motion readings to medical practitioners or care givers. A typical body area network kit will consist of :
2. a Processor,
3. a transceiver and
4. a battery.
“The skin contact resistance will usually be between 1000 and 100,000 Ω, depending on contact area, moisture, condition of the skin, and other factors.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/
Can you measure body resistance with a voltmeter or digital multimeter?
Excerpt from this Physics forum link: "a DMM is not considered a good way to measure such a high impedance reading like skin conductivity. A typical Galvanic Response Sensor (GSR) has the ability to adjust filters/rates and is optimized for high impedance measurements to reduce the signal to noise ratio. DMM's will often pick up environmental noise on very high impedance circuits (including probe motion across changing surface contact impedance)."
Can you measure body voltage with a voltmeter?
During low-humidity weather, scuffing of shoes upon rugs can put a huge voltage on your body. It is fairly easy to detect this voltage (try RIDICULOUSLY SENSTIVE CHARGE DETECTOR) However, this voltage is fairly difficult for students to measure. A normal voltmeter won't work: the electrical resistance of a normal voltmeter will discharge your body almost instantly (it places a 10-megohm resistor across a 200pF body capacitance, and by T=RC we calculate that the meter's resistor drains out your body's stored energy in two thousandths of a second.)
Body voltage determination