I'll leave it to others to suggest a dedicated device but I will point out that there's a fantastic FREE program which all crossword addicts ought to have on their computers.
It's the one which I use to compile crosswords myself and it's incredibly useful for solving them too!
The dictionary function provides definitions, synonyms, hypernyms, hyponyms, antonyms and more.
The wildcard function is great for finding all words which will fit a given pattern. (For instance, give it '?a?e?t?d' and it will offer caseated, gazetted, lacertid, lamented, parented, patented and talented. Double-clicking on a suggestion then gives you its definition).
The anagram function gives you all words which can be made from the string of letters you provide.
Worth a look, perhaps?
http://www.sequencepublishing.com/1/thesage.html