I've tried several different apps on both apple and android platforms. I thought android had the best one. But since my meter can download the data to my comp, I now use that software instead. It takes more time inputting data at times, but the standard day/week/month models are invaluable in determining dietary changes.
If you use an iPhone a very excellent app that I found is called "lose it".
The app is for weight loss purposes but works very well when trying to do LCHF, eat low sodium, or work on carb-fat-protien ratio. It has a wonderful database of foods that you can either search by name or barcode, I find that the easiest.
I've used Diabetes Buddy with the iPad, iPhone and iPod Touch at one time or another and highly recommend it but am pretty much sticking to my Contour USB at present. For my android device I've tried a couple of different apps but IMO I just don't think they have the same polish as the ones for Apple devices (YMMV).
I don't have an app for tracking BG because my pump uploads everything to a web-based site, but I do use the Lose It app, as mentioned above, on my iPhone. It is quite good, but find that I need to use at least 2 other apps to ensure to greatest access to nutritional data.
Calorie King and MyFitnessPal are the other two apps I use. Each of the 3 apps will at times have what the other two can't find. Calorie King is the "old standby" with a basic interface and more generic foods. Both Lose It and MyFitnessPal offer recording meal data (as well as other things) and the bar code readers are great for not having to type anything. Over the recent past, I found that MyFitnessPal has expanded their database so that it's been able to find more things than Lose It. It also has Canadian-specific food items in its listings. What I like about Lose It was one time I scanned a bar code on some brown rice and while it couldn't find the specific brand it showed nutritional data on generic brown rice that matched what was given in the Calorie King app.