In terms of writing a term paper on cell phones, the thesis would depend upon specifically what you plan to write about.
In terms of your introduction and thesis statement:
Indicate your topic. When you write an introduction, you need to clearly indicate the topic (i.e., the subject matter) that you will be writing about. Be careful that you do not confuse your topic with your thesis. For example, if you are writing an essay that argues for renewable energy, you will need to briefly explain or define renewable energy because that is your topic.
In deciding upon the specifics you will include, you mention that you will write about history of the cell phone: will you also include the advancements of cell phones most recently, and what extended services and perks are included with new cell phones and related services? Or expectations of the future of cell phones?
Will you include possible dangers of using cell phones, especially concerns of driving and texting and/or talking while driving, or concerns about potential brain cancer?
Depending upon the extent of your research, your thesis statement would vary. If you are only going to include the history of cell phones, you might write:
The heavy, bulky portable devices of the past have given way to amazing little computers that do more than allow one to talk on the phone. (I try not to use "phone" more than once.)
The development of cell phones has changed the face of the world, how people communicate, and obtain information.
Another spin on a broader topic might look like this:
While cell phone have advanced in amazing ways since their inception, there are many concerns about their safe use.
Hope these suggestions provide you with some options and/or ideas.