First I found a list of Norwegian words on the net. I should have taken the effort to get hold of the same word list as Wordfeud is using. The list was loaded into a table using SQL Developer.
Say you want to see if there is any word that start with N and uses only the letters C, F, S, and A. The following SQL may find it:
where regexp_substr(word,'^n[cfsa]+$') is not null ;
For those not familiar with regular expressions, well, just Google or check out any good book on Perl. In short, the ^ and $ means the beginning and end of line (word in this case) respectively,  is used to create a group of letters; [cfsa] means any letter of c, f, s, and a; + means one or more occurrences.
Now I only need to make a mobile interface to this, and create a function that calculate the score for each word based on Wordfeud's rules. Next Christmas, maybe. I do know there are apps ready to suggest this, but that is not half as fun :-)