Diskeeper would be a way to degrag the physical database files and then use DBCC REINDEX to rebuild the indexes.
A search on Google for defrag SQL shows a couple of articles about this
If you are comparing it to the defragment tools such as the utility software used to defrag the hard disk drive, it somewhat different to an SQL database. Remember that it is a database it is really risky to perform defragmentation to the SQL database. However, I believe that there is no software that defrags an SQL database or any database.
diskeeper is not going to defrag anything in the database. That is at the filesystem only. in order to defrag your indexes you will need to implement a maintenance plan to do so. You can use the builtin plans or you can use a script that is smarter then the maintanance plan wizard in order to do so. This is a great one that is smart and is free. The developer has done a great job on this but be sure to test it first.