There are a number of applications out there that offer some form of SEO help; obviously some are better than others.
1. SEO Stats
SEO Stats is a great application for all levels of SEO's, and is free! This application is particularly great for checking your ranking. Not only can you check your page rank, but you can also check the number of Yahoo baclinks, and even .EDU OR .GOV backlinks. It is also a very useful tool if you would like to see how many wikipedia links you have, and check your progress on compete.com.
This application comes in two different forms. You can either download the lite version, or the pro version. The pro version is going to cost you $2.99. It will definitely be worth it. This will give you not only the ability to check your google analytics, but also your AdWords, and AdSense. This is very important for tracking all the organic traffic your site may be getting. Also this is a great tool to always know your page views, visit counts, and different bounce rates day to day.
3. QuickSense
For individuals who have multiple sites running that use google AdSense this application is perfect for you. Throughout the day you can check multiple site's different revenues and number of clicks throughout the day. This is a great way to estimate profits and see which strategies are working the best. QuickSense is going to cost you $3.99, so unless you already have some AdSense in place I wouldn't recommend wasting the money. However, if you do have adds in place, be sure to pick this one up.
This application is what it is all about for SEO's. SEO Search Ranking lets you monitor the position of certain keywords you are trying to rank for, and doesn't limit you with CAPTCHA codes. You will know the exact position you are ranking for with each site and this is in the end, what you are always trying to do. This app is going to cost you $1.99 in the app store, and is well worth the couple bucks. One downside of this app is that if your keywords are not matching you for the top 64 in Google's search engine, then you really can't even use it. Then again, if you are not in the top 64, you have a lot of catching up to do.
Apple has come a long way with their products. Nowadays they have a healthy platform for developers to produce great applications for everyone. This now includes some pretty great apps for SEO's. Be sure to take advantage of this, you do not want to be left behind, and checking your SEO on the go is going to be essential in our technology driven time period.