ive used duct-taped foam on the bars, and zip ties with foam facing the screen to secure my S4 before. cheap and effective; never an issue. did it maybe 3 or 4 times.
then again i also secured two 10 foot kayaks to the roof of my RX-8 with pool noodles, cut up cheap foam mattress pads, and ratchet straps, with 2 bikes hanging off the rear on a crappy cheap trunk bike rack i got for free.
same trip; tail of the dragon from deals gap north carolina (with some spirited driving on fun curves; wickedly fun sports car and a legendary fun twisty road) all the way up to halifax nova scotia, and we biked kayaked and camped all over the place along the way.
you dont always need the latest and greatest gear; a roof rack, kayak mounts, and bike rack would have set me back $1200, and we absolutely wanted to take our RX-8 for the trip (mind you we did ditch the kayaks and bikes at a friends to get a nice fun run one way, then loaded them up, checked, tightened, rechecked, and STILL had a blast thru the twisties with them on the car on the way back) plus all my photog/video gear in the back seats and trunk stuffed with camping gear.
if you'll use it all the time, buy a couple, try em all out back to back, see which works best, and return the rest. for us, that was a one-time thing and while money was not an issue, i didnt want to waste $1200 on roof rack and bike rack for a car i will never again drag bikes or kayaks or camping stuff, that i would never be able to sell. plus it was fun taking a sports car all ghetto rigged when we have a perfectly good capable stick-shift 4Runner, but its not nearly as much fun to drive in curves.