This is dangerous unless one monitors the temperature on said thermometer without hesitation. One distraction and you have a dangerous situation. (fire!)
A gas stove on high can put out 40,000 btu/hr! With an electric element you would need ~ 11,700 watts! A far cry from the 800-1300W found in small electric fryers.
Temperature will obviously plummet when a frozen mass of potatoes is added! This is why commercial fryers switch R2B (put the pedal to the metal!) and can keep up. Ding! Fries done!
Those turkey fryers that you see in those "I burned the house down this Thanksgiving" videos can go as high as 250,000 btu/hr on high fire using propane! Oil will become overheated very rapidly with this kind of input and will start an extremely dangerous flash fire. Panic and destruction follows shortly thereafter.