It's no accident that Apple chose a yellow icon for its walkie-talkie feature. I dug out my old (2002ish) Nextel with PTT (push to talk). It was all the rage back then... :
Nextel i880 - Review 2007 - PCMag UK
Motorola i355 Nextel Walkie-Talkie Cell Phone NEW in Open Box | eBay
Motorola i series i730- Black (Boost) Cellular Phone Walkie-Talkie Nextel | eBay