1. A method of detecting a fall by a user, the method comprising: with a processor or computer, processing measurements obtained from one or more sensors to extract a respective value for a plurality of features associated with a fall, wherein processing the measurements includes processing measurements obtained from an air pressure sensor to extract values indicating changes in altitude; with a processor or computer, determining a respective log likelihood ratio for each of said extracted values; with a processor or computer, determining whether the user has fallen based on the determined log likelihood ratios; and with a transmitter, in response to determining that the user has fallen, transmitting a signal indicating the user has fallen.