I liked this sensible answer:
"Can I Pray With an iPhone?"
I agree that an actual, physical siddur "has a certain sanctity to it that a virtual siddur cannot attain," but perhaps this is because we're a lot more accustomed to the technology of the book, with 500+ years of history and associations behind it. I wonder if praying from Gutenberg's invention didn't shock a few parchment scroll fans back in the day, as well.
Also agreed that the point of prayer is to escape form the tyranny of e-life. But prayer in a synagogue is communal and, paper siddur or not, will not exclude that loud, off-key guy who thinks his "Amen" must be heard in the shul down the block. "Ask the Rabbi" offers this solution to the electronic version of barriers to concentration:
"The ring tone issue is easily solved by switching to vibrate. Notifications can be turned off in Settings. But you're still going to have those incoming calls and text messages popping up over your siddur. To avoid these, the only trick I know is to switch to Airplane Mode. It seems to me that this is a must for proper praying. Look, if you can do it on the runways of Planet Earth, you can do it on the runway to heaven as well."