Hi Elliott .....
There is a great deal of research going on related to the cause of acoustic neuromas. According to the presenters at the last ANA Symposium a year ago, to date, the research shows no direct correlation between cell phone use and I would have to presume wi-fi, as well ..... since it is even farther removed from ones head.
So far, the only known cause for acoustic neuromas is large quantities of ionizing radiation. BUT, there are many, many ANs that have formed with no known cause so that leaves open many other possibilities or just random growths.
That being said, it would serve us all well to live as healthy a lifestyle as possible, e.g. reduce stress, get plenty of sleep, eat good quality natural/organic foods, etc. However, we do not live in a "bubble" so many environmental factors are out of our control.
Just remember none of us on this forum are researchers or trained medical professionals, so we are sharing our collective personal research.
Best wishes. Clarice