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.
https://www.gotenna.com/pages/gotenna
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!.
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