On one hand, we enjoy those advantages. First, we can communicate with people all over the world. Second, smart phones are quite light, and it is easy to carry them anywhere. Third, in case of danger, we can use it to make emergent call.
On the other side, smart phones do bring some disadvantage for us. Apart from its harm to our health, it also make our class uncontrollable. Most students like to bring smart phone to the class. and then, they cannot resist the temptation of communicating with friends, which distract them from focusing on class.
As a teacher, we must find some effective way to deal with smartphone. It can help ESL students to look up the meaning of the word at handy, on the other hand, most of them may play games during the recess and communicate with friends frequently.
Here are some useful links for smartphone in class.