Police will send a bluetooth message to mobile phones in the centre of Peterborough later, one week after a 16-year-old boy went missing.
Theo Kawala was dropped off in the city centre by his father for a night out with friends at 1930 GMT last Friday.
Police divers have been searching the River Nene in the city.
Officers will hand out leaflets and send an appeal for information to phones within a 22.8m (75ft) radius of the police's sending device.
Police will also visit bars, pubs and clubs to talk to people on a night out, and be on the route between the city centre and Theo's home.
'Get in touch'
Late on Friday and shortly after midnight, Theo had walked along Broadway and then Westgate, before walking through the bus station and along Bourges Boulevard.
He then crossed Bourges Boulevard at the pelican crossing near the old Woolworths building and walked into Lower Bridge Street.
Theo, who is slim and 6ft 1in (1.85m) tall, was wearing blue jeans, a black shiny jacket, a red and white check shirt and black trainers.
Insp Mat Newman said: "Our aim is to reach those people in the city centre who may have also been out last Friday and may have some important information for this inquiry.
"We know that he walked past several groups of people and we would like these people to get in touch."
Anyone with information should contact Cambridgeshire Police.