FROM_UNIXTIME(somefield)
can be compared to CURDATE
() assuming you're using MySQL
SELECT * FROM mytable WHERE FROM_UNIXTIME(datefield,'%Y-%m-%d') = CURDATE();
ETA:
Okay, I was assailed by doubt when this answer was marked down. So I went and did a couple of tests. Given MySQL it definitely works. So why the downmod?
Consider this test which outputs 2 identical fields for every row in a table:
SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(CURDATE()),'%Y-%m-%d') a , CURDATE() b
FROM tablewithsomerows
WHERE FROM_UNIXTIME(UNIX_TIMESTAMP(CURDATE()),'%Y-%m-%d') = CURDATE();