I would check your receiver on our wireless alarm the panel illuminates each time a sensor is activated wether armed or not, so a useful way of checking it is working or if the battery is flat. Other than that without the led in the PIR you have no quick way of telling. I only have a PIR in the garage but find it reassuring to see it flash each time I enter the garage. As for intruders seeing it I think few will even notice unless looking directly at it. You are more aware because you know it is there.

Richard