I have the breadwallet app on my iPod. I also have it on my iPhone. Now if I use the (iPod) recovery phrase on my iPhone's breadwallet app, will both apps work or is the phrase valid for just one app at any given time?
Your funds are stored on the bitcoin network. Your recovery phrase is your key to access those funds. You can make as many copies of that key on as many devices as you like and access the funds from any one of them. (This is also why it's important to keep your recovery phrase secret, and never type it into other less secure devices like a laptop, don't take a photo of it, don't send it in an email, etc. Write it down on paper and keep in a safe place.)