Synchronized vibrations The gold standard for calibrating a human body is the intentionally-healing touch of a caring,embodied human being whom one trusts, i.e. a "mother's touch" or its equivalent. That touch (and sometimes any human touch at all) is hard to find, so there is also value in solo sources of vibration.
But healing through self-massage runs into the same paradox one faces when tickling oneself: the most sought-after effects come from vibrations which are novel and thus cannot be anticipated. That problem faces most mechanical sources of vibration as well, like "vibrators," because the source is too regular and predictable. (Even electric candles and fireplaces which look real actually produce the same stored, random-looking pattern over and over again, and like other digital technologies present the appearance but not the statistical substance of natural input).
If one seeks organic entropy, the best available sources are natural sources of turbulence. The naturally occurring "chaos" in turbulent flow is in fact sometimes used for random-number generators, so there is no way your nervous system will get bored with it, and almost no way for a mechanized source (such as a hypothetical "Evil Ad-server") to manipulate that signal. Turbulence is the safest mechanical source of stimulation available.
A fire outside is the best (like our cave-man ancestors enjoyed), followed by a fire in a fireplace. A slow-motion visual light-source could come from a lava lamp, or a plasma ball with the jagged blue lightning-tendrils inside. For sound, jets of air (or sometimes fans) make naturally coherent entropy.
But the best source of entropy-stimulation, by far, is the jets inside a hot tub. Not only is hot-water immersion systemically relaxing, but it suspends the body in near-zero gravity. Furthermore, an underwater jet is a localized source of both pressure and vibration, in principle aimable at any sore spot, its genuinely chaotic, multi-scale vibrations penetrating the myofascial tissue, synchronizing on the skin, and coursing across the body in coherent waves. Ideally, the sore spot can be tensed and relaxed while the jet is on it, allowing the jet's high-entropy vibrations to mix with the body's self-generated ones.
Home-brew healing methods Toward the goal of creating a smooth, left-right symmetric motor map, there are many, many forms of healthful, private self-stimulation:
Foam rollers, whose localized pressure-spots sensitize mechanoreceptors and thereby "illuminate" a local sensorimotor region. Especially good is the "rumble roller," whose soft spikes create even more localized and penetrating sensitivity. The challenge for an individual is dealing with the discomfort, which is downright painful at first, and sometimes feels physically threatening. The best way to become familiar enough with these sensations to distinguish healing from injury is to practice, first, on the skull. Myfascial "adhesions" (or "virtual adhesion" in my language) on the skull can be both uncomfortable and healing when released. And they have the additional advantage of being thoroughly non-threatening; there is little chance of damaging a joint when pressing on the skull, not matter how much it might hurt.
Showers provide a good source of high-entropy sensation, the longer the better. Hot relaxes muscles and cold tenses them; both can be useful.
Skin-brushing and caresses (especially from someone else) feel good because they provide the most high-entropy source of spatiotemporally coherent information possible (each bristle is a point, but each point moves in a straight line).
Lying on one's back on a hard wood floor creates simultaneous tactile sensation on the entire backside, which is an invaluable way to validate internal proprioceptive signals. Hard floors provide higher-frequency feedback (and hence higher information flow) than soft carpets or spongy surfaces.
Standing upright with one's spine against a pole provides the same kind of signal validation as lying on the floor, but now with sensation directly on the (midline) vertebrae rather than the (laterally separated) muscles of the back. No particular effort is necessary; standing still is good enough to help.
Yoga, Pilates, Feldenkrais, Tai Chi, and other self-motion disciplines act effectively as self-calibration protocols. Practicing the same whole-body sequences repeatedly (and one hopes properly as well) provides a consistent baseline regimen, against which progress and changes in sensation can be noticed.
Dance, especially unscripted autonomous dance, is an outlet with which a brain can generate whatever self-motion it desires. Such dance in the company of others (as in contemporary "movement meditations" like Open Floor and Ecstatic Dance) creates several additional benefits: the motions of others serve as new sources of entropy; each individual feels accepted in autonomy rather than conscripted by regulation; the collective shares group resonance. In fact, collective wordless dance is probably the closest approximation available today to the "proximity synchronization protocol" our primal ancestors used.