Crosswarn offers users to use Zello for $8.00 per month per user.
If users do not wish to use a regular Raspberry Pi site, they may also use a Zello Patch. A Zello Patch works by connecting Zello to a two-way radio, the connected radio will then transmit the Zello traffic to other two-way radios connected to it. While a normal site requires a P25 Phase I capable radio, a Zello Patch can be anything from analog to OpenSky, as long as it has Voice Operated Transmit, or VOX available. A Zello patch site is $8.00/month.
Requirements:
Android device with 3.5mm headphone jack
Zello cable (3.5mm to *your radio type*)
Example: Zello to Motorola XPR/APX
A VOX-capable radio.