I've looked at many callerID apps and only found one so far that will place a button next to the number of a caller - whether they are currently ringing your phone, or a missed call - that will drop off the phone number into google and do a search. The one I found does this, but it is pretty much useless since it formats the phone numbers as XXXXXXXXXX instead of XXX-XXX-XXXX. With the former returning a small number results (usually from useless spammy reverse lookup sites that seem to be popping up all over the place).
Complaints with the current batch of reverse lookup/CallerID apps center around how many numbers these days are cell numbers which are not published in databases like white pages/yellow pages/411 etc... However, people post their cell numbers in lots of crawlable content, such as blogs, facebook messages, craigslist ads, etc.... I can't tell you how many "unlisted" numbers I've resolved to names/addresses/businesses/scams by searching the number on google. However, it must be formated correctly to get useable results.
This would be a "must have" app - even if it only worked with missed calls by simply copying the number into memory, then pasting it into the google search box and hitting enter - 3 basic steps to a killer app!