There is some science behind the Rev-X. Can't speak for the Hot Shot's as I haven't done/seen an analysis on it. Following is a copy of a post of mine from another site.
No magic here. Just science.
Rex-X primarily consists of three main ingredients: Boron, Potassium and Calcium. All three are known additives and have been / are used in various lubrication applications. The cost of the additives make them prohibitive to mass marketing. Rev-X seems to have found a niche market with daily driver diesel engines. Particularly those that are short cycled or idle for extended periods of time.
Boron -- Borated compounds have been used with good success for some time as lubrication additives. They have excellent low temperature characteristics and reduce the coefficient of friction resulting in lower wear rates.
Potassium -- Simply said, it's a detergent. Effective at "cleaning" the lacquer and soot left behind in the nooks and crannies of the injectors.
Calcium -- A detergent also. Not as effective as Potassium but, still useful.
One thing to remember. If you use Rev-X and perform Used Oil Analysis', you must let the lab know. One of the reasons Potassium has not been used as a consumer oil additive is its presence is an indication of coolant in the oil. A competent lab will call these levels of Potassium a coolant contamination.
IMO, Rev-X is a great product. Anecdotally, there are numerous folks that have used it with great success. Those that weren't successful likely passed the point of no return and have mechanical damage or other issues. Scientifically, well, it just works. No magic.