I don't know about an app but do have a solution for any phone which has a web browser installed to enable a (non-updatable) copy of a database to be carried/viewed.
Last September I decided I was carrying too many devices in my pockets so bought a Nokia E63 smart phone (which comes with office applications, calender etc.) to replace my previous cell phone and Palm Tungsten PDA. The Nokia is a great device but the one thing it didn't replace was the LDS/PAF Gedcom viewer software which ran on Palm OS. I'd looked around once or twice and found that there is nothing on the market for the Symbian OS but recently it struck me that the phone has a web browser and I still have the Ged2www program which I used to use to generate web pages from a Gedcom file for use on our web site.
I created a new Gedcom file from my database, ran Ged2www and then copied the results to the Micro SD card in the phone. All I need to do is open the base page and it automatically opens the browser so that I can navigate through all my data.
It obviously doesn't offer update facilities but neither did the program I ran on the Palm -which is fine by me as I only want the data on the phone for reference.
There are other programs (e.g. Ged2html) which will generate web pages from a Gedcom file. Google will soon find the various sites for downloading the software.