I was surprised to find out about the character 餵 (wei4, 喂) because it doesn't seem to have a meaning other than an expression to answer the telephone. Since the telephone was only invented in the last hundred years or so...this must be a relatively new character. Is this accurate? If so, how was the character/sound developed?
喂 means feed(verb) originally besides answering telephone.
Regarding the origin of the character, according to CiYang
(1) (餵、喂是近代的“餧”字) 喂食 餵 and 喂 are modern writing of 餧 餧,饲也。——《玉篇》 餧 means feed(verb)
It's a new character derive from 餧.
P.S. The most popular usage of 喂 may be a character for answering phone. But it is also a derivative from the common usage of saying hello in a rude way. Because of this, in fact, there are many people claims that answering phone with 喂 is impolite, we'd better say 你好/您好 instead. If you call public service number like customer service hot lines, you always hear the operator answering 您好.
喂 being used for answering the telephone in modern times seems to be a
未解之谜, one idea is that the usage might derived from French
日语：もしもし，(发音 moshee moshee)
法语:Allo ,oui (发音 wi)
德语： Guten Tag，Tag
意大利语： Pronto? Ciao.（俏）
西班牙语：Aló。.Sí, diga. Dígame. Bueno. 或者aló + buenos días(早上好) 、buenas tardes(下午好)、 buenas noches(晚上好) 葡萄牙语：Aló
餵 and 喂 were different characters. Both of them are so-called 形聲字, which can be roughly translated as meaning-sound character. It means that part of the character is for the meaning, and part of it is for the sound.
For 餵，食 is its 形 part, or the part for meaning, which has something to do with food, and 畏 is its 聲 part, which sounds wèi or ㄨㄟˋ. For 喂 the 聲 part is the same as that of 餵 which is why they share similar pronunciations, and its 形 (meaning) part is 口, which has something to do with the mouth.
餵 can only mean to feed or to raise (a pet); 喂 could (past tense) only mean to make some sound (to scare off). 《康熙字典》 has an entry for 喂:
That's why 喂 is used for telephone answering. It can be also used to shout out to someone to raise attention, as "hey" in "Hey! You stop there right now!" The simplification of Chinese characters turn two characters into the same thing (which I consider bad ): so now 喂 can mean to feed too.
There's also an entry in 《康熙字典》 for 餧, an alternative character of 餵:
So… basically to directly answer your question, 餵 doesn't answer the phone, 喂 does and also inherit 餵's meaning of to feed or to raise pets.