for your consideration, the best sms/call blocker i've ever used is MCleaner, it's available for Symbian, Android, iPhone

if you're at lost when thinking of what features should you put, just look at that apps. the only drawback from that apps is no pattern matching (incl predefined pattern ie. number containing letters, number less than 'n' digits, etc)
and instead of blacklist and whitelist, there should be another profile that is "silent". blacklist will ignore the sms/call entirely, remove it from inbox and log, but save a backup internally. while silent only prevent the tone from playing, stop the led notification, silently reject the call but anytime you open the phone, you can still see unread message/missed calls (yes this can be achieved by using silent profile, but it can't reject calls nor stop led)

btw when will you release a preview/alpha/beta build?