I'm sorry to be harsh on this person but this is quite a dumb post. What is the difference between hacking a celebrity vs an ordinary person? None.
Any penetration testing / security consultancy will be able to do what you're asking for, provided you can pay their rate.
> Does this service exist? If not, is this a million-dollar start-up idea?
No it is definitely not a million-dollar startup idea. It also wouldn't be a startup it would be a consultancy. Penetration testing firms can easily charge clients up to around $1000 / day. How many individuals are going to pay multiples of $1000 to see how secure their online data is?