GrayKey was detailed on the MalwareBytes blog back in March and works on iPhones, including the most recent iPhone 8 and iPhone X, up to at least iOS 11.2.5. (Whether it works with later versions of iOS is unknown.) A $15,000 version of GrayKey requires an internet connection and allows 300 unlocks, while the $30,000 version cracks as many iPhones as you would like.
In 2016, the FBI demanded that Apple specially write new code so that the agency could get into an iPhone used by one of the married shooters in the San Bernardino terrorist attack. Apple refused, which resulted in a long and ugly battle between Apple and the FBI over user privacy, which the FBI ultimately dropped when Apple wanted to let it go to court and the FBI found a (possibly Israeli) company that could get into the shooter’s phone.