I'm still just messing around with Pluto on some old computers while I'm building a nice core and media directors. After messing around a bit, i'm seeing some things that would make great additions to the Pluto system:
1) Voice Recognition - No, not completely interactive with microphones all over the house, but streamed from a cell phone or PDA (see 2 below)
2) BLuetooth Wireless Headset (for cell phones) - use this for the follow me as well as voice commands. For instance, most BT headsets have a button that you can press and hold while saying someones name for voice dialing. It would be nice with Pluto if this feature could be used somehow to send voice commands to the core. Also, if the BT headset could be tied into Asterisk, that would be amazing - it would be like wearing your phone on your ear all day - you would never miss a call.. Add this with the voice recognition and then you can be talking on the phone, hit the button on your ear to flash, then say the name of the person in the house to transfer the call to. Tons of possibilities here
3) Keep an eye on the nintendo Wii remote drivers - once they get it fully working, it would be a great "wireless mouse" for MD's. Kind of early right now, but i think it would be an amazing feature to have.
4) To Do Lists - I think Pluto can be more than just for Home Entertainment and automation - it should also help organize your life. A centralized To Do list would accomplish just that. When something is on your mind, put it on your To Do list. Then, each day when you turn on the TV, a reminder is given for items that aren't yet checked. Text and audion would be nice features
5) Going along with #4, some time of Reminders - scheduled daily, weekly, monthly etc.. Kind of like a cron system to remind you to pay your bills each month, change the furnace filter, etc...
6) Again, going along with helping organizing ones life - a nice calendar system. Again, it would be an easy and convenient way to manage your appointments, schedules, etc.
7) Music Visualizations (maybe Pluto already has this??)
Printer connectivity system - print out your To Do lists, print serve for your home PC's, print out your calendar, catalogs of your media, etc...
9) I know, not practical, but the MD and orbiter menu system - switching to HTML would make it much easier for users to make their own menu systems. (supporting PHP, javascript, etc)
THese are just off of the top of my head, I'd like to hear others feature suggestions....