A method of monitoring the usage of an internal combustion engine comprises performing an engine monitoring routine using a local monitoring device attached to an internal combustion engine. The engine monitoring routine includes generating data representative of a plurality of vibrations of an internal combustion engine using a vibration sensor of the local monitoring device, processing the generated data to determine a first value representative of a firing frequency of the internal combustion engine, generating an aggregated summary based on the first value and transmitting the aggregated summary and identification data for the local monitoring device to a remote application. The remote application processes the transmitted aggregated summary based on the identification data to determine engine speed usage data.