In reading Tour de France articles about stuff - not results, I ran across Ice Vests. Made me think of this thread. For time trial warm-ups, so likely not good for long rides. every little bit helps.
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from Cycling Weekly
OK, this last one isn't bike tech, but it's still an important performance product for time trials. Across the team paddock on Wednesday, with the sun searing towards 30°C, ice vests were commonplace on the backs of riders readying themselves for their roll-outs.

Keeping core body temperature down is crucial to prevent overheating, and stop riders from 'blowing up' during the effort.

Tudor squad is supplied ice vests by Dutch company Inuteq, who also provide products to runners, footballers, and even MotoGP motorcyclists.