Where did u find this info?well i haven`t heard about it but in theory it sounds fairly easy to measure.I can imagine a closed container filled with hydrogen H2 placed in a strong alternating electromagnetic field to create a plasma in it.It could be a coil with the container in it.All this would have to be placed in the caloriemeter(coil+container) to measure the temp increase.Given off heat would have to be compared with the electrical input of the coil.I think the whole thing will have to take also the radiated waves into account.
Other thought would be the plasma made by an electric arc,but i am afraid there would be some reactions with the electodes,that may affect the energy readings.
Anyhow,what kind of energy was released?
On the other hand during the electrolysis the first product is H+ that gets combined with another H+ creating a H2 molecule close to the cathode.So we have here a release of the energy somewhere.Maybe someone can figure out if its possible to measure it from this perspective.
Or a way of capturing this bond energy to assist electrolysis.It could be also true that electorlysis in the electric arc (as some people here are making) has something to do with this extra energy claims.H+ is more reactive than H2 so the burning of it in oxygen may be somehow faster.To destruct the H-H bond u need energy,the same would be true for O-O bond.Now suppose we burn directly the splitted H in slitted O.Energy of the reaction may be greater then burning of the H2 in O2,because in burning of H2 in O2 a part of the energy released is being used to split H2 and O2 into ions(before they combine into water).During burning of H+ in O2- the molecules are already splitted so the flame can have higher temp.That is because there is no energy stolen into splitting.Smaller effect would be when burning H+ in O2.Here some energy would go for splitting of O2.
Now it could be that the person who made the claims of the higher energy release confused the burning of H+ with burning of the H2.In that case the H+ flame would have higher temp,but the plasma creation needs also energy so the net result would be the same in both cases.