Mobile router by a mobile phone

During late 90's or early 2000's probably, I was working for Ericsson on mobile telephony, thus I was kind of familiar to mobile phone. At that time we only had DSL Internet with telephone cable to a modem and Ethernet cable connected many computers in house from room to room. Probably we had laptop, too, but very expensive.

Perhaps we were working for data channels [similar to datacom for a computer network] for a mobile phone [GPRS] at that time. Suddenly I looked at my desktop PC and wondered if we could use a mobile phone as a mobile modem to a PC or perhaps laptop. This way we would be able to get Internet anywhere we went. We didn't have WiFi or Bluetooth at that time.

[By the way, I couldn't recall many things clearly.]

Now we have WiFi, thus a mobile phone connected to wireless telephony networks could offer Internet WiFi as a mobile router to other devices like a tablet.

* Is this hard to do? I guess, "No". All technologies are there. Only to combine or integrate those.
-> a mobile phone does have WiFi already to connect to a home WiFi router.
-> a mobile phone could connect to wireless telephony Internet.
-> tons of WiFi routers available for home users.
-> mobile phone's OS is like a computer OS, i.e. powerful enough.
-> Anyways there should be something like WiFi protocol stack and 2G/3G/4G protocol stacks. We could use those to develop applications to offer mobile router on a mobile phone.

Btw, having good applications to offer better life to people is a better option for engineers and scientists.

* By the way, a mobile router would be a good device for entertainment with affordable cost. However it would give those crazy out there more tools to attack others. What else could we say?

* I knew that many mobile phone users would select unlimited data plan if a mobile router is available.

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2018-12-09: In those days, perhaps in the '90s, I saw something on the web and thought about having web phones to communicate with others worldwide for free.

Around the same time as thinking about asking corporates such as Ericsson to give spare capacity to use for Internet communications to their local offices. For example, Ericsson had offices in Australia, England, Mexico, USA, Canada, Germany, etc. by connecting calls using their connections to route calls from Canada to those countries, we would only pay for local calls instead of long distance. Anyway, back in those days long distance calls was so expensive even within Canada. Now users have lots of Internet phones to communicate with each other for free.

- Our dial-up 56 Kbps at home was very slow

- Ericsson's network was so fast.