Found it! | The Ultimate Dictionary.
Well it's not exactly a dictionary but it can help you when changing your words into infinitive or conjugated form. I have been looking for something like this for a while because I prefer writing new verbs in Infinitive form and maybe you do too. You just type in whatever new verb in either conjugated or infinitive form and the website engine lists the infinitive form and all conjugations in every tense. It's great help.
If you enter 'suis', it gives you the verb 'suivre' and does not mention 'être'. The same thing happens in the 'conjugueur' of WordReference (http://www.wordreference.com/conj/FrVerbs.aspx). But in the French-English dictionary of WordReference, you will obtain a better result: http://www.wordreference.com/fren/suis. You can then click on 'conjuguer' to see the full conjugation of either 'suivre' or 'être'.
I know an app like that, but it's only for Spanish words. It can tell you the definition and conjugation. It's called SpanishDict if you're interested.
The reference in France is the Bescherelle book of conjugation. All students have to buy one, and I still have mine (1978 edition)!
They now have a website: http://bescherelle.com/conjugueur.php
Once you see the conjugations, you have to click on the buttons on the right to switch from active to passive, and from simple to compound tenses.