One way is to cofigure a small PLD. Another way is to use 74HC30 type 8 input gate and then invert the output with a 74HC04 type gate. A third way is to buffer each of the 8 signals through 74HC07 type open drain type buffers and then interconnect all the 8 outputs together with a pullup resistor. This wired method is called wired-OR. A fourth way is to eliminate the use of INT0 and have a timer interrupt on-board the processor instead poll your P0 port on a periodic basis and note if the value from the port indicates any sensors active.

Michael Karas