Having a few devices on different platform means that you will probably want to be able to access the same information instead of keep two or more disparate sources of information. Examples of these information include tasks and notes. Of course, other common information would include email, calendars, contact and files.
Out of the box, both iOS and android platform would have already supported most email platforms natively, calendars using google calendars and files using dropbox or sugarsync.
For tasks, you would likely be sync-ing up using google tasks, and for notes, you would probably want to sync your iOS notes with android ones.
To Sync up your Google Notes (e.g.your ideas, thoughts, information that required storing for future reference)
1. Set up a sync on your iPhone, under the Calendars settings. Make sure you turn on Notes sync.
2. Once this is done, you will find that there will be a new account show in your notes application. Your existing and new notes created will be synced with google notes.
3. On the android device side, I recommend android applications such as GNotes from the Google Play. (url is https://play.google.com/store/apps/details?id=org.dayup.gnotes).
To Sync up your Google Tasks (e.g. to-do list, shopping check list etc):
1. For iOS platform, I recommend downloading gTasks from the Apple appstore, as the application is simple to use. https://itunes.apple.com/us/app/gtasks-hd-google-tasks-go/id428249408?mt=8
2. For android platform, I recommend GTasks. https://play.google.com/store/apps/details?id=org.dayup.gtask&hl=en
One note: Make sure you use a common google account for all this work! =D