Probably have to use two power supplies. If your sensors have analog outputs, you're going to have to put them through an A to D converter to make use of them anyway.
Use an LM339 quad Comparator or an LM393 dual Comparator. They work well on a single supply. The output is a TTL/CMOS compatible open collector output which can be pulled up to whatever Vcc your processor is running on. If you look very carefully they may even have single comparators in a SOT23-5 package. Be careful you don't have both of the inputs outside the common mode range. With a reference at V+/2 this should be no problem if V+ is in the 9-12Volt range. Don't forget the bypass caps on the comparator either.
Well if it's a digital ouput from the sensor, that is it is either 9v or 0v then a simple voltage divider of say two 10k resistors should work. CMOS ouput to top of top resistor, common voltage of both sensor and micro to bottom of bottom resistor and micro input connected to where the two resistors hook together. That should give you a 4.5v input to your micro.....