Here are some great iPhone/iPod Touch apps that, while not strictly “Zen”, they do help to calm the mind (or at least remind me of my time in Japan). You’ll find these all in the iTunes App Store:

Koi Pond — beautifully done with sounds accompanying the koi (Japanese carp). Feed them, scare them (my two year old loves that), or just watch them swim around. $.99
iZen Garden — you are your own monk at a famous rock garden. Rake the stones however you desire. Shake to reset. (There are several of these type of apps now, ranging from free to $2.99.)
Bloom — from Brian Eno, this musical and visual app treats you to a break through subtly-changing, repetitive sounds and images. This is great to hook up to speakers as background music while you work. $3.99
Bowls — can’t afford a $300 Tibetan “signing bowl” but love that droning, melodic sound? This app lets you “play” several different bowls as a way to relax your mind. $1.99
iBonsai — grow your own beautiful bonsai plant in seconds, then, move it around, shake it to remove leaves. Snap a picture and email to a friend. Then repeat… $.99
iKoto — the sound of the koto for me is very relaxing. So to have the ability to play a portable koto wherever you go — with some songs already pre-programmed — is a great way to take a mental break. $1.99
Easy Relax — choose where you want to go and let the sounds of your new “environment” relax you. From Hawaii Vacation to Fishing Time, Blossoms from India to Jungle, all within your reach. $.99 (There are many of these ambient sound apps available, ranging from free to $2.99.)
TanZen Lite — OK, this isn’t actually relaxing. It’s a game. And it can be a damn challenging game at that. However, it reminds me of staying in an ryokan in the mountains with my wife and one of these games was there. We sat watching the snow on the mountains in the warmth of our room silently playing this game.

There are apps for Chakra, meditation, Buddhism, you name it and there’s probably an app for it…

Hopefully you could find something that might help you stay in peace…