A stroke detection system operative to detect strokes suffered by mobile communication device users, the system including a hardware processor operative in conjunction with a mobile communication device having at least one built-in sensor. The hardware processor is configured to, repeatedly and without being activated by the device's user, compare data derived from the at least one sensor to at least one baseline value for at least one indicator of user well-being, stored in memory accessible to the processor and/or make a stroke risk level evaluation; and/or perform at least one action if and only if the stroke risk level is over a threshold.