Get a GoTenna - it allows you to send text messages and share GPS locations on offline maps with others. goTenna Mesh sends messages via a 1-watt UHF radio transmitter. The range is in the order of up to 3 miles (4.8 km) in open terrain, and up to a mile (1.6 km) in congested terrain.
They now have a range of products right up to the Pro @ $500 with 60 hours battery life. It operates on any frequencies in the 142-175 MHz (VHF) & 445-480 MHz (UHF) ranges. Note some products are quoted for delivery in late August and may not be available in your country.
Another mesh unit, Sonnet, is currently in Kickstarter mode - campaign closes Tue, August 1 2017 3:01 PM BST.
$89 for a pair, available November, ships anywhere!.