Electronics these days are tending to move away from using magnetism to operate. It was really only ever bad for things like TVs and old CRT monitors. Things that relied on a very precisely calibrated magnetic field to control the display of the image. Floppies also used magnetism to store data, and most hard drive's still do, but cell phones use LCD screens and solid state storage as a general rule.

Nothing in an LG Chocolate should be relying on a precisely calibrated magnetic field to operate, and SD cards don't store data using magnetic principles either as I recall.

I don't remember if Apple's iPhone is using purely solid state storage or if it's still using the miniature hard drives, but if it's the latter, you'd want to be careful of prolonged exposure to strong magnetic fields. That would be about the only cell phone I can think of that might present you with a problem.