No phone carries an electrical current strong enough to worry about being electrocuted by one. There are situations in which you can be electrocuted through a phone -- but the odds are on par with getting struck by lightning (literally).
Weak Charge, Covered in Plastic
It is implausible that you will be electrocuted by any type of phone, because you are mostly gripping components made of plastic (unless you are still using a tin can). Even if you were to grab the internal hardware of a phone as it rings, the electrical charge would not be enough to do you harm -- phones use a small fraction of an amp. A normal household wall outlet provides 15 amps.
A person can be electrocuted by a land-line or a charging cellphone if lightning strikes either the phone line or the electric line supplying that outlet. This is the worst-case scenario -- most houses have "ground" wires that direct such currents away from the house, and these wires would have to be cut or damaged.
Keep Your Cells Dry
Don't get a charging cellphone wet. Anything that is plugged into an AC outlet can do you harm if you dip it in H2O. Water conducts electricity quite well -- and so do you.
- Photo Credit telegraph pole image by Alison Bowden from Fotolia.com wireless phone image by timur1970 from Fotolia.com