I've done a modern CoC game before and made it work. There are some delicate balances to be considered as Minipainter mentions but one of the most amusing things about CoC when run well is that all the resources in the world don't matter much in the face of the Mythos.
If your players are resorting to rocket launchers to solve their problems, chances are that they've already failed or that they're about to make things much worse. The old joke was that the elephant gun was the most worthless item in CoC because all it did was draw more attention to yourself which you do not want.
Cell phones and internet can seem like potential issues (and can be if the GM isn't mindful), but there are many ways to allow them without ruining the game. The most powerful contrast in a modern CoC game is that while the PCs may not be as physically isolated as they would be in an earlier era game, they are still as socially and intellectually isolated. Just remember that when the PCs cry to the police that they've just been attacked by zombies with tentacles coming out of their ears, they are probably going to be incarcerated and sent to the nearest rubber room.
Likewise, there just isn't going to be much use for the internet (other than as a way to help the PCs figure out where to visit next) when you're coming up against forces that defy conventional concepts of "reality". The only people that could speak any insights of the Mythos would be the insane and to understand the ramblings of the insane generally requires a similarly unstable mind. In short, Mythos ramblings will mean very little to a "sane" person until they open their minds to the maddening truths therein, which consequently drives one insane.
So it can be done and even opens certain adventure opportunities that don't exist in other CoC eras. But the GM just needs to be aware that the PCs will try to make use of different types of resources and be prepared to handle those situations appropriately.
HARRY DRESDEN — WIZARD
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