MicroUSB connected devices.
I don't have any MHL cables to test the XPERIA M with but have tested the following microUSB connections and found them to all work.
The one exclusion here is the Sony DK10 LiveDock™ multimedia station
which only provides power. It can NOT provide data and power over one USB connection with default XPERIA M configuration.
This does not bode well for any MHL connection.
• Aten 4-Port USB 2.0 Switch
• Targus Desktop USB 2.0 7-Port Hub
• WDC 320GB USB 2.0 HDD connected via powered USB hub.
• Logitech USB Unifying Mouse M950, M905, M235 and Keyboard K400, K800 tested
• HP v165w 8GB flashdrive
- Voltage required ~4.5-5.5VDC. This will not work on a Sony XPERIA S due to power requirements, BUT works OK on an XPERI M.
• SD/MMC card reader and USB 2.0 ports on a Dell U2410 24" IPS monitor
• Tested a few SanDisk and HP 8-32GB USB 2.0 FAT32 flashdrives and all have worked.
• Galaxy Note Connection Kit. Model: DR03-S2 provides microSD, SD and USB flashdrive access. A must have!!! But, only supports one(1) connected peripheral at a time, so can't have Keyboard/Mouse and microSD card all connected at the same time...pity. But this can be done via powered USB 2.0 hub.
There is also the Sony Miracast™ Wireless Display IM10
which probably should be tested when it's more widely available.