Two men and three women were driving from the university city to London on the afternoon of November 4 when the raiders struck, Thames Valley Police said.
They took the watch and the victims’ phones, before forcing one of them to transfer the cryptocurrency out of their account.
The victims were left in the Five Mile Drive area of Oxford.
Detective Sergeant Stuart McMaster said: “I am appealing to members of the public who may have seen anything suspicious or have footage of three vehicles in some specific locations in Oxford and Kidlington.
“We want to hear from you if you saw or have footage of either a black BMW saloon car, a blue Hyundai Ioniq or a silver Mercedes Benz Vito in the area of Yarnton Road and Sandy Lane, between Kidlington and Yarnton, or in Five Mile Drive, Carey Close, Rotherfield Road and Kirk Close in Oxford between 1pm and 4pm on Tuesday November 4.
“Thames Valley Police has been conducting a thorough investigation into the offences.
“This has included house-to-house, CCTV, automatic number plate recognition, digital, forensic, cryptocurrency and financial inquiries.
“We have also conducted warrants in London and Birmingham along with arrests in Kent, arresting four men.
“We are supporting the victims and keeping them updated during our complex investigation.”
Officers arrested a 21-year-old man from London on suspicion of conspiracy to commit robbery, kidnap and other driving offences, and bailed him until January 14.
A 37-year-old man from London was also arrested on suspicion of robbery and kidnap, and bailed until January 30.
A 23-year-old man from Kent was arrested on suspicion of robbery and kidnap and was bailed until until February 7.
A man, 19, from Birmingham who was arrested on suspicion of robbery, kidnap and possession of articles for use in fraud was bailed until January 29.
Police are appealing for anyone with information or relevant footage to contact them, quoting investigation reference number 43250563760.
To remain anonymous, contact Crimestoppers on 0800 555 111 or online.