Nimbostratus
CirrocumulusIn answer to your first query you can use Priority Group Activation. Have the two pool members in two pools and the priority of the pool with member one will be higher than the pool with member two in it. That way whilst member one is up all traffic will go to this member. When it fails then member two will receive traffic.
Not sure i follow your second question but a HTTP monitor allows you to GET for a particular URL in the Send String and you can configure the Receive string for the expected response.
Hope this helps,
N