Autocom Eurocom - The Eurocom offers driver-passenger intercom, along with the ability to interface music, radar detector, and 2-way communications. I have my Valentine 1 radar detector and Motorola StarTAC cellular phone tied in, and I can quickly switch out the cell phone for an FRS 2-way radio. I also have a portable AM/FM/CD player for commutes. See my Autocom page for more information.
BMA
airBag Tank Bag - This ingenious tank bag is the ONLY model I have
seen that TOTALLY PREVENTS any scratching of your tank. The bag mounts
to a hinged base, fastened to the top four screw holes surrounding the fuel
filler. The bag "hovers" over your tank, with no straps,
clips, etc. to fiddle with. Fueling couldn't be simpler - just lift,
and the bag swings up out of the way! The airBag is rather narrow and
tall, with rigid sides. There are several pockets on the inside,
including loops for 35mm film canisters. The bag is a heavy grade of
Cordura nylon, but is not waterproof - a nice fitted rain cover (with clear
top) is available. Other options include a drink holder, external
clip-on accessory pocket, and double-sided map pocket. Installation
was a snap, but the bad news - the bag prevents me from using my StreetPilot
on the mount I have designed, and the cell phone interferes with the bag
when raised for fueling. Look for NEW installation reports &
photos on those items soon - I'm moving everything around! (Note - BMA
does plan to introduce some more accessories for this system, including GPS
mounts! No word on when these might be available).
From a usability point of view, the bag is good for daily use. I keep
gloves, earplugs, etc. in it, so it's large enough for my purposes. It
is rather narrow compared to most other bags, presumably so that it won't
interfere with the bars at full lock. It stays put when riding better
than any other bag I've used, and refueling is EASY (I know I already said
that, but I refuel at least 2-3 times a week & I hate moving tank bags!)
I would like a larger bag on extended trips, but this works just fine for
90% + of the time. Perhaps a "Deluxe" version with a
teardrop shape (fatter toward the rider) could be made available - I've
suggested that to the vendor.
Garmin StreetPilot - For a bike as large as the R1100RT, the StreetPilot (or the ColorMap; same thing with a color display) is the ultimate choice for GPS navigation. It's large display is easy to read, and has several levels of backlighting for use any time of day or night. By downloading maps from the MapSource USA discs, detailed street-level maps for any region in the USA are presented, along with the ability to search for "Points of Interest" (POIs) by address, type, or proximity. POIs include everything from auto parts dealers and gas stations to national parks and restaurants. For smaller bikes, the Garmin eMap offers most of the same basic features in a much smaller package.
Kisan TireAlert - Do
you check your tire pressure before every ride? How
about during? Did 
you pick up a nail in that gravel parking
lot? Kisan Technology's tireAlert system constantly monitors
both front and rear tire pressure. The display will start flashing if
the pressure in either tire drops by 4psi, and a 6psi drop sets off red
flashing lights. This is an excellent safety device. I
also have their PathBlazer and TailBlazer products (headlight and brake
light modulators) installed. Check out my installation page on the
tireAlert here.
R-A-M Mount for
GPS -
GREAT mounting system for GPS, or just about anything
else! These products are REALLY secure, and it's easy to move the GPS
between bike and car. I have a R-A-M base and a power cable in each
vehicle, and just loosen the handle on the bracket, move it to the next
car/bike, tighten it up & plug it in. They are available at my
accessories site, Cycle
Gadgets.
I have a page detailing installation of the GPS mount here.
RCU Products Parcel Shelf - from BMW
of Salt Lake. This handy shelf mounts above the instrument cluster
and below the windshield, and makes a great place to mount radar detector,
cell phone, FRS, walkman, garage door opener, or just about anything
else. You can see how I'm using mine here.
Throttlemeister
Throttle Lock - Nicely made throttle lock, works well as bar-end
weights too. A little on the cumbersome side to use - I'd prefer a
true cruise control like this
one, but it's not available for the R1100RT yet and apparently not
likely ever to be - click here
for text of the E-mail to Carl Byrne on the subject. If you're willing to pony up a $100 deposit on
a ~$700 cruise, let them know - if the get enough interest, they will revive
the project!
Valentine One Radar Detector - Without
question the finest radar detector made. The V1 is not only more
sensitive than most, it also offers the unique features of displaying the
number of radar sources seen, and indicating whether radar is coming from
the front, rear, or side. The V1 gives the rider valuable information
that is lacking in all other detectors.