I never really thought about that. There is a possibility but I seriously doubt it. I mean if you keep your phone near your computer, it doesn't really get damaged. I bet it's the same with your tamas.
Thanks guys for clearing this I think I got this from my dad cause he is always obsessed not to leave my phone next to flat screen tvs and I was applying it also on tamagotchis xD
No dont worry it will not harm the tamagotchi in any way (infact my phone has been sitting by my tv for the longest time and nothing happened the tv us 5 years old at least.)