There are two available from the Android Marketplace but Family Bee
which can be the cheapest only reads the gedcom file and returns a reasonable display - there is a trial version available for free from the Marketplace - better to try before you buy.
Family Bee requires you to transfer a copy of your gedcom file to the sd card on the phone but the latest update added the facility to also access your gedcom file from Dropbox
(an online storage and synchronising facility) which means that the file can be shared between your machines and that they are using the most up to date version of the file.
The other main one is Gedstar Pro
The android app is free but unless you are using the program The Master Genealogist (TMG) you have to purchase a converter program (Windows only) which converts your gedcom file to a database format. The display and search facilities from this are excellent although purchasing the converter makes it twice as expensive as Family Bee. There is also a time limited trial version available.
My only quibble with this app is that it does not use your gedcom file but its own database format which means that any changes to your gedcom file mean that the database has to be re constructed and transferred each time.
Family Bee http://www.mobilegenealogy.com/family-bee/
Gedstar Pro http://ghcssoftware.com/android/index.php
My own preference is for Family Bee and this is simply down to the convenience of using the linked Gedcom file although I do prefer the layout etc of Gedstar Pro.