We demonstrate that a cheap (30USD) small, low power 8x8 thermal sensor array can by itself provide a broad range of information relevant for human activity monitoring in home and office environments. In particular the sensor can track people with an accuracy in the range of 1m (which is sufficient to recognize activity relevant regions), detect the operation mode of various appliances such as toaster, water cooker or egg cooker and actions such as opening a refrigerator, the oven or taking a shower. While there are sensing modalities for each of the above types of information (e.g. current sensors for appliances) the fact that they can all be detected by such a simple sensor is highly relevant for practical activity recognition systems. Compared to vision (or thermal imaging systems) the system has the advantage is being less privacy invasive allowing it for example to monitor bathroom activities (as shown in one of our evaluation scenarios). The paper describes the sensor, the methods used for activity detection and the evaluation.