Abstract: An apparatus (10) for detecting flow of a fluid (11) in a conduit (12) is disclosed. The apparatus comprises means (44) for inferring the flow of fluid based on a change in temperature of the conduit over time. The means for inferring the flow of fluid may comprise a neural network model. One or more other environmental parameters may be used in addition to temperature. The disclosed embodiments can allow an estimate of the flow of fluid in the conduit to be obtained using a low-cost, low-power and/or non-invasive device.