Tybalt Melia of Snowdonia is in the final of CBBC's 'My Genius Idea' with a safety device which lets cars know when they're approaching a cyclist.
Bike Bleeper transmits a message to a car radio so a suitably equipped driver will be given an audible warning that there's a cyclist ahead.
"I invented the Bike Bleeper because a friend from school got knocked off his bike and killed," Melia told the BBC.
"So I thought if I invented this, it might prevent a number of cyclists' deaths."
A prototype is on the large side but Melia reckons it can be made small enough to fit on handlebars.
"I know I need a specific signal and to change the device from 30 to 50 metres so you get a good warning if travelling at a fast speed so you've got time to slow down."
When he was seven, Melia won a Welsh young inventors' competition with a portable seatbelt for children on buses. He also invented a thermometer for his sister to wear on her arm, to slide up and down to show how cross or pleased she might be with him.
The winner of the show will be announced on 7th December.
Devices of this nature have been produced before but, as they rely on motorists fitting the devices, take-up is minimal.