So far my experience with my Nexus 7 C70 was wonderful. The only thing missing is 3G connectivity. To overcome this shortcoming, I've been scouring on the net, try to find is there any solution available for it and found out one application called
PPP Widget which works as expected.
Infos from the developer forum only stated Huawei or ZTE modems, finding a compatible modem was a quite challenging. Today, I bought a Huawei 3G modem to try it out to see if the application able to link up my Nexus 7 to the 3G network.
The requirements are...
1. Root access is mandatory
2. "Superuser" app needs to be installed (usually comes with rooting tools)
3. Needs at least Android 3.1 for automatic mode, 2.2 for manual mode
My setup...
1. Faux Kernel 011m
2. AOKP Build 3
3. Chainfire SuperSU
4. Samsung OTG cable
5. Huawei E353 HSPA+ modem
The Result...

Not bad for Saturday night traffic with 2 signal bars
» Click to show Spoiler - click again to hide... «


PPP connection log, for those who are interested...
CODE
ATZ
OK
AT+CFUN=1
OK
AT+CGDCONT=1,"IP","unet"
OK
ATD*99#
CONNECT
Report from chat: Â Sep 29 22:38:49 CONNECT
Serial connection established.
using channel 2
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB0
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x74bdf97c>]
rcvd [LCP ConfReq id=0x3 <asyncmap 0x0> <auth chap MD5> <magic 0x2fb049f> <pcomp> <accomp>]
sent [LCP ConfRej id=0x3 <pcomp> <accomp>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x74bdf97c>]
rcvd [LCP ConfReq id=0x4 <asyncmap 0x0> <auth chap MD5> <magic 0x2fb049f>]
sent [LCP ConfAck id=0x4 <asyncmap 0x0> <auth chap MD5> <magic 0x2fb049f>]
rcvd [LCP DiscReq id=0x5 magic=0x2fb049f]
rcvd [CHAP Challenge id=0x1 <fc8d3aad3cf43fdfa401bcdfbc2810b0>, name = "UMTS_CHAP_SRVR"]
sent [CHAP Response id=0x1 <39451a48acfe7d0c109d5cb7bf75ae13>, name = "maxis"]
rcvd [CHAP Success id=0x1 ""]
CHAP authentication succeeded
CHAP authentication succeeded
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns3 0.0.0.0>]
rcvd [IPCP ConfNak id=0x1 <ms-dns1 10.11.12.13> <ms-dns3 10.11.12.14>]
sent [IPCP ConfReq id=0x2 <addr 0.0.0.0> <ms-dns1 10.11.12.13> <ms-dns3 10.11.12.14>]
rcvd [IPCP ConfNak id=0x2 <ms-dns1 10.11.12.13> <ms-dns3 10.11.12.14>]
sent [IPCP ConfReq id=0x3 <addr 0.0.0.0> <ms-dns1 10.11.12.13> <ms-dns3 10.11.12.14>]
rcvd [IPCP ConfReq id=0x0]
sent [IPCP ConfNak id=0x0 <addr 0.0.0.0>]
rcvd [IPCP ConfNak id=0x3 <addr 10.14.188.124> <ms-dns1 58.71.136.10> <ms-dns3 58.71.132.10>]
sent [IPCP ConfReq id=0x4 <addr 10.14.188.124> <ms-dns1 58.71.136.10> <ms-dns3 58.71.132.10>]
rcvd [IPCP ConfReq id=0x1]
sent [IPCP ConfAck id=0x1]
rcvd [IPCP ConfAck id=0x4 <addr 10.14.188.124> <ms-dns1 58.71.136.10> <ms-dns3 58.71.132.10>]
Could not determine remote IP address: defaulting to 10.64.64.64
local  IP address 10.14.188.124
remote IP address 10.64.64.64
primary  DNS address 58.71.136.10
secondary DNS address 58.71.132.10
Script /data/data/de.draisberghof.pppwidget/app_bin/ip-up started (pid 15475)
Script /data/data/de.draisberghof.pppwidget/app_bin/ip-up finished (pid 15475), status = 0x0
Terminating on signal 15
Connect time 4.7 minutes.
Sent 4347150 bytes, received 8472817 bytes.
Script /data/data/de.draisberghof.pppwidget/app_bin/ip-down started (pid 16688)
sent [LCP TermReq id=0x2 "User request"]
rcvd [LCP TermAck id=0x2]
Connection terminated.
Script /data/data/de.draisberghof.pppwidget/app_bin/ip-down finished (pid 16688), status = 0x0

wow great post...now nexus 7 also can use 3g...that's good new eventhough need 3g modem like china brand do, but still can use 3g...can u post details on how to install and setup the device as easier as u can...hope u can help...