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... :
Motorola Nextel i355 Direct Talk - Walkie Talkie PTT | eBay
Nextel Mobile | StartEngine
Nextel Launches the Motorola i850 Camera Phone
Motorola i355 Nextel Walkie-Talkie Cell Phone Push-To-Talk NEW in Open Box | eBay
Nextel T320 Two Way Radio & Smartphone - YouTube
Throwback Nextel! | Best mobile phone, Best mobile, Phone
Direct PTT - Get The New Nextel i682 Two Way Cellular... | Facebook
Direct PTT - The Nextel T320 is the full package. This model is a Smart- Radio with PTT & 2-Way Manage your entire fleet from your palm with full GPS Tracking and Mapping.
Direct PTT i655D Two Way Global Network, Analog & DMR All In One Global PTT Radio | Eventtone