The Federal Motor Carrier Safety Administration has amended Federal Motor Carrier Safety Regulations to establish minimum performance and design standards for hours-of-service electronic logging devices along with requirements for the mandatory use of these devices by drivers currently required to prepare HOS records of duty status.
While the rule does not explicitly exempt agriculture, most farmers and ranchers should be exempt from the ELD requirement due to existing HOS exemptions for covered farm vehicle drivers. ELDs automatically record driving time, monitoring engine hours, vehicle movement, miles driven and location information. 
The ELD final rule permits the use of smart phones and other wireless devices as ELDs, so long as they satisfy technical specifications, are certified and are listed on the FMCSA website.