i have a siddur app on my ipod touch. it has saved a few times when i forget to bring a siddur. i’ve used it for bentching, tefillas haderech. i’ve used tehillim app for my daily tehillim if i find myself w/ a few minutes here or there. i also have igeres haramban saved on my ipod as a pdf and have used it too.
have i davened off my ipod? yes. did i feel like i was davening? no. i felt odd davening off a device i use for school and entertainment.