accessories that can be connected / added to iPad 2 & iPad 3

Can I connect an external mouse & keyboard to an iPad2
or iPad3?  I can still type faster on a conventional keyboard
that touch screen (even a virtual keyboard in a touch screen
is much slower to type on compared to conventional keyboard).

can I connect a mouse to an iPad?  Perhaps not a USB or is
there a 3rd party 'wireless mouse' for iPad out there somewhere?

if for some reason I wanted to connect my 3G external modem to
an iPad, is this possible?  I've seen WiFi broadband router which we
can connect a few USB 3G modem and Windows laptops can connect
to the WiFi service broadcast by this broadband router which accesses
the Internet via the 3G USB modem(s) connected to it.  Anyone can
suggest any specific model of such modems that are battery operated
& as small as possible (possibly palm-size or smaller, just like those
little Huawei ones).  Or is there any PDA mobile phone (models & the
required apps) that can offer such WiFi service (so I can use my mobile
phone as sort of broadband router/gateway for the iPads) : does an
iPhone offer such feature?  I find it not so worth it to pay US$180-200
more to have a built-in 4G modem for iPad3.

Can I have a microphone (& earphone) connected to an iPad2/3 & then
make phone calls using the iPad if the iPad has a SIM card (is this a
microSIM just like the ones needed for iPhone ?)?  What app is needed
to enable the iPad work as a phone?
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1. yes you can connect bluetooth keyboard or mouse. i have tested the apple keyboard mouse. can connect bluetooth mouse.. i have already connect apple magic mouse so i know..non apple may not connect.

3. any modem then can provide wifi access can help you connect to internet. ipad itself does not have any port so only option is wifi modem

4. you cannot make normal calls from ipad. just voip calls using softwares like gtalk
Michael MillerPresidentCommented:

These are some good questions.  To best understand Apple's stance on these issues it is good to understand their philosophy.  They decided to keep their system closed.  With Android, you have full control to tinker around with the way things work.  With Apple they have designed the iPad from the ground up in a way that keeps Apple in full control.  With this in mind, here are some answers for you to consider:
Q1:  Keyboards are supported.  Apple supports Bluetooth keyboards (the Apple wireless keyboards will work) and an Apple Keyboard Dock that slides into the data port to fully control the iPad.  
The advantage of the wireless is that you can keep the iPad in any orientation (portrait, landscape).  The disadvantage is you have to find some way to prop the iPad up while you type (I like the Bluetooth keyboard setup they have that is built into a folding cover for the iPad like these ).  This cover opens up and acts as a stand for the iPad while you type).
The advantage of the iPad Keyboard Dock is that the keyboard acts as a prop for your iPad so you don’t  need anything else to view the iPad while you type.  The downside to the Keyboard Dock is that you can only us the iPad in portrait orientation.

Q2:  No mice for the iPad.  Apple doesn’t have a system to support a mouse cursor on the screen in the home environment.  I checked with some apple developers and they said there is no such functionality.  The concept of the iPad is to keep things touch screen.
Q3:  To get a USB air card working with the iPad you would require a router like a Cradlepoint CTR35.  Unfortunately I can’t find any of these routers with a battery, so I don’t think it is a good option.  
In my opinion the best option is using a portable hotspot.  These devices are available from every carrier and have great flexibility.  Most of them allow for 5 devices to connect to it which means you can also use it to supplement your cell phone if need be, give wifi to your laptop, your ereader or any other wifi enabled devices you carry around.  This option requires only one contract and then you don’t need any other devices for internet.  I use a Verizon Novatel MiFi 2200 (they now call it the Jetpack SCH-LC11).
You can also use your smart phone as a hot spot, but I don’t like this option as much.  You asked for models, but the list is too long.  iPhone 4 and 4s work as hotspots as does every current Android phone. This requires an extra charge from your provider.  The problem is that if you are in a 3G only area and you get a phone call you lose the internet if you take the call.

Q4:  You can use headphones and make phone calls from the iPad, but not like an iPhone.  They iPad won’t make a cellular phone call, rather you have to use a Voice over IP solution (VoIP) like Skype or a host of others.  As they say, “there is an app for that”.  I personally use Skype, but I know there are others like Fring and Truephone.
The new iPad (to Apple there is no such thing as an iPad3) has FaceTime built into it which allows you to make video calls to other Apple users (you can call camera enabled iPods, iPhones and other iPads).

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