Ralink 5350

http://wiki.openwrt.org/toh/start

VC0706 RS232 CMOS serial port Camera board

http://www.hametech.com/html/product/view2-24-49.html

OpenWrt-HAME-MPR-A2

HLK-RM04无线路由器/串口转以太网/串口转WIFI模块

HAME MPR-A1 3G行動電源路由器

MPR-A1 3G無線路由器+移動電源 可供IPAD充電 迷你3G路由wifi

RT5350F AP 整套方案 SDK4.0 搭好環境fedora6和vmware 直接可用

https://forum.openwrt.org/viewtopic.php?id=42142

New!!!!!! Support OPEN-WRT RT5350 flash 4M and RAM 16M wireless router with Captive Portal/ODM service

I've been playing with these modules a bit and I have discovered a few things.  There are a number of undocumented AT commands in the stock firmware.  Here's the full list of them:

Channel
CLport
default
dhcpc
dhcpd
dhcpd_dns
dhcpd_ip
dhcpd_time
err
escap
excxxx
Get_MAC
gpio_mode
gpio_read
gpio_save
gpio_write
net_commit
net_dns
net_ip
netmode
net_wanip
out_trans
pm
reboot
reconn
remoteip
remoteport
remotepro
S2N_Stat
save
settings
settings_done
status
suspend
tcp_auto
tcp_client_check
uart
uartpackintertimeout
uartpacklen
uartpacktimeout
ver
wifi_conf
wifi_ConState
wifi_Scan
XON_XOFF

The most interesting of these is at+excxxx, its just a call to system() with the argument you provide.  You can start telnetd with it to get a shell.

at+excxxx=telnetd

You can also get a shell on UART2 by sending the special sequence "174317529705122" and return.  getty sets up the port for 57600 baud and waits on this sequence before its allowed to accept characters and output anything.  login has already issued the "login:" prompt, so after entering the sequence, you won't see anything until login asks for the password.

I've documented the above already in the wiki, including a bit on TFTP, check it out.

Here's a couple of handy resources not referenced here yet:

A schematic of the HLK starter kit V1.7 PCB in this zip: http://m5.img.dxcdn.com/CDDriver/CD/sku.214540.zip
The manual for the module in English is here: http://www.hlktech.net/inc/lib/download/download.php?DId=19

Cheers!