Gshock metal square (like the photo I referenced) never failed on me (and I have 3 of those in different colors: gold and silver lcd ones, and black memory in pixel new one)
Though even if you consider any possible harmfull effects like thyroid nodules formation correlation [1] (people somehow only think about ionizing radiation, but there much more that happens in a cell that can be possibly disrupted without xray level stuff to damage dna or heat: there are ion channels and what have you), the Bluetooth on gshock — if set up — will work only for a few seconds twice a day. Basically nothing even if you sleep directly on it all night long