There are companies like G Force where you send your ECU to and they reprogram it with a higher rev limit and send it back to you. I don't know if there is another way except for stand alone engine management. Of course if you need the car it is important to remember there will be down time while the ECU is in transit and being worked on.
Don't have the answer for a save rev limit, most of the time I don't think the stock turbos (at least U.S. spec ones) will be able to take advantage of extra revs anyway. Some guys with singles take the car up 8k rpms so who knows?