A method comprising: connecting, by a mobile device, a voice call for a user of the mobile device, wherein connecting the voice call causes one or more radio frequency transmitters of the mobile device to transmit radio waves at a first power level; obtaining, by a motion sensor, motion data describing movement of the mobile device; obtaining, by a proximity sensor, proximity data describing a proximity of the mobile device to a detected object, wherein the method further comprises: determining whether the mobile device is on the user's body or on an inanimate object based on the motion data and the proximity data; and adjusting the transmit power level based on the determination whether the mobile device is on the user's body or on an inanimate object, wherein adjusting the transmit power level comprises: determining that the mobile device is on an inanimate object; and in response to determining that the mobile device is on an inanimate object, adjusting, by a baseband module, the transmit power level from a first power level to a second power level, the second power level being higher than the first power level, wherein determining whether the mobile device is on the user's body or on an inanimate object comprises: determining a motion state of the mobile device based on the motion data; determining a proximity state of the mobile device based on the proximity data; and determining whether the mobile device is on the user's body or on an inanimate object based on the determined motion state and the determined proximity state, characterised in that the motion data comprises a signal corresponding to an acceleration of the mobile device over a period of time; and wherein determining the motion state based on the motion data comprises: calculating a first value indicative of a power of the signal within a first frequency band; calculating a second value indicative of a power of the signal within a second frequency band, wherein the second frequency band is greater than the first frequency band; and determining the motion state of the mobile device based on the first value and the second value. connecting, by a mobile device, a voice call for a user of the mobile device, wherein connecting the voice call causes one or more radio frequency transmitters of the mobile device to transmit radio waves at a first power level; obtaining, by a motion sensor, motion data describing movement of the mobile device; obtaining, by a proximity sensor, proximity data describing a proximity of the mobile device to a detected object, wherein the method further comprises: determining whether the mobile device is on the user's body or on an inanimate object based on the motion data and the proximity data; and adjusting the transmit power level based on the determination whether the mobile device is on the user's body or on an inanimate object, wherein adjusting the transmit power level comprises: determining whether the mobile device is on the user's body or on an inanimate object based on the motion data and the proximity data; and adjusting the transmit power level based on the determination whether the mobile device is on the user's body or on an inanimate object, wherein adjusting the transmit power level comprises: determining that the mobile device is on an inanimate object; and in response to determining that the mobile device is on an inanimate object, adjusting, by a baseband module, the transmit power level from a first power level to a second power level, the second power level being higher than the first power level, wherein determining whether the mobile device is on the user's body or on an inanimate object comprises: determining a motion state of the mobile device based on the motion data; determining a proximity state of the mobile device based on the proximity data; and determining whether the mobile device is on the user's body or on an inanimate object based on the determined motion state and the determined proximity state, characterised in that the motion data comprises a signal corresponding to an acceleration of the mobile device over a period of time; and determining a motion state of the mobile device based on the motion data; determining a proximity state of the mobile device based on the proximity data; and wherein determining the motion state based on the motion data comprises: calculating a first value indicative of a power of the signal within a first frequency band; calculating a second value indicative of a power of the signal within a second frequency band, wherein the second frequency band is greater than the first frequency band; and calculating a first value indicative of a power of the signal within a first frequency band; calculating a second value indicative of a power of the signal within a second frequency band, wherein the second frequency band is greater than the first frequency band; and determining the motion state of the mobile device based on the first value and the second value.