I also come from a country where mosquito bites are an annoying issue too. I don't like to use mosquito net and also mosquito repellent coil too. I have tried the power guard product you mentioned, with a few brands, and another type of electric mosquito repellent product which emits light to attract the mosquitoes. I also tried to use essential oil. I think they worked for a while, but then stopped working. I am not sure if the mosquitoes here are just too smart or I haven't find the right product to get rid of them. I used to turn on air con, but it isn't a good idea. Now we just put the fan to full blast and hopefully the mosquitoes won't get to bite us too much. I am interested to find out more about anti-mosquito sonic repellent and hope it works.