I am very doubtful about this.
Warmth or heat alone can not generate electricity, what is needed is a temperature difference.
If one side of a peltier chip is warm and the other side is cold then electricity can be produced.

In the case of a flashlight the heat from the users hand is unlikely to work well.
In hot weather with the suroundings at near blood heat there wont be enough temperature difference.
In cold conditions the user would probably be wearing gloves and/or have cold hands at far below blood heat.