All muscle cells have electrical activity associated with their activation. This applies equally to the striated cells of large skeletal muscles that are activated by conscious intent, as well as the smooth muscle cells of internal organs that operate more autonomously. Most people will be familiar with the electrical signals of the heart, in the familiar repeating pattern of an EKG or ECG (electro cardiogram). These signals are strong enough to be easily measurable on the skin with very simple electrodes attached to the surface. But all muscle action is controlled by electrical activity, and so allows the possibility of observing and recording that activity with appropriate sensing devices.
Researchers have been studying the tiny electrical signals generated by the small and large intestines and stomach for several decades. Using internally placed electrodes they have discovered the intrinsic behavior of gut organs. Different researchers have used different naming conventions, but there are in general just a few types of activity. Physically there is mixing, slow propulsion, and rapid propulsion. Mixing occurs when a section of the organ contracts, and nearby sections do so also but at random times. Propulsion occurs when the contractions are synchronized, so that the material is forced to move along. Electrically there are "slow waves" and "spike bursts". whereas the heart beats at about one time per second, or 1 Hertz, the slow waves are much slower, and are measured in terms of cycles per minute (cpm). The stomach has a slow wave normally around 3-4 cpm. The colon (large intestine) and small intestine slow waves are just as slow under certain circumstances, but can also be as high as 30-40 cpm. Different sections of the small intestine have different intrinsic frequencies, while in the colon the frequency depends less on the location and more on what it's doing. Very slow waves in the colon are associated with mixing of the contents, while higher frequencies result in propulsion.
Here are some interesting papers related to myoelectric science:
"Colonic Motility - From Bench to Bedside"; Sushil K. Sarna, Morgan & Claypool Life Sciences; 2010
"The Burden of Selected Digestive Diseases in the United States"; Sandler, GASTROENTEROLOGY2002;122:1500-1511
"The Burden of Gastrointestinal and Liver Diseases, 2006"; Shaheen, Am J Gastroenterol 2006;101:2128–2138
much more to come...