Can civirules be triggered off a custom field of type date for eg Date equals Now
You are on the right track with using now in field comparision. See my Question and Answer here. 


trigger: daily trigger for group members 
condition: field value comparison for a date, datetime or timestamp field, where you can use any string recognized by the php function strtotime. So you should be able to use now as explained in the PHP documentation. In your case i would use "+5 days" as the comparison value.


After saving the condition the description should show Contact.custom_127 = 2016-05-19 (date when you saved the condition.)

Hint: use the latest CiviRules from Github, as support for timestamps was added a few days ago.