http://fma.sourceforge.net
I'm using it and it does what you describe.  Here is an excerpt fro
FMA's page

Fma: It's Magic

Hi Guys

If you own a T610 and a computer, go out and buy yourself a bluetoot
USB adapter (less than 40 US$), and go to the source forge website an
download the latest version of FMA and its associated programme float'
media control. It's free

This is what you can do with FMA

1. Ordinary things like browse through the files in your cellphone
and transfer files to and from the cellphone (pictures, themes and mid
files). Midi songs are small files. You can send a certain number o
them to the phone, and use a hands free set to listen to music while o
the move

2. Write your SMS from the computer and send them. This is a
advantage since it is easier to write from a computer keyboard. Als
receive your SMS directly to your computer. Save your old SMS in th
harddisk for later reference
To send and receive SMS, you don't need to press any button on th
cell phone. You just leave it in its corner, and you do everything wit
your computer

3. Make and receive calls from your computer. You must of course hav
a headphone, and enable audio gateway on your bluetooth programme. I
you have pictures of your friends, you can link them with their phon
number, so that when they call you or when you call them, you see
small semi-transparent window pop up with their picture. I like thi
feature. You can record the conversation in your hard disk if you want
Again, no need to press anything on your phone. Just leave it alone

4. Organise your phonebook in the computer (again, it is easier to d
it on a computer keyboard), and synchronise with the phone. If you hav
your phonebook in Microsoft outlook, this is how you can import it t
FMA: with the programme that came with your phone (XTND connect), yo
synchronise your cellphone with outlook, and then you synchronise you
phone with FMA. You then edit the phonebook with FMA, add pictures an
customised ring tones to your best friends numbers, and synchronis
with your phone. This works very well, believe me. FMA writes a lo
that tells you which changes were made to the phonebooks in th
cellphone and in FMA

5. Write notes in the computer and save them in the phone: ban
account number, passwords, car registration, etc..

6. Activate and edit a profile for your phone on the computer. You ca
also switch off the cellphone from the computer

7. Phone keypad (under tools menu): you can take full control of th
phone from the computer. For example the cellphone is in the sittin
room, you are in the bed room with the computer (if your house is no
too big), you can, from the computer, take a picture, and view it i
the computer, so you can see on your computer what is going on in th
sitting room. For example to see if a visitor is worth your attention

8. The best now, and this is magic! I had never seen such a thin
before, and I don't understand why SE doesn't mention it among th
features of T610
You can control the PC from the phone. Unlike other remot
controllers, you have here a menu appearing on your cellphone. You ca
scroll up and down the menu using the joystick

-You can move the mouse pointer using the joystick, right and lef
click, select and click anything. This requires you to look at th
computer monitor so you can see where to move the pointer

With the following features, you can switch off the monitor to sav
power, since a menu appears on the cellphone
-You can switch off, hybernate or put on stand by the computer fro
the phone
You have a menu on your phone saying "hybernate", "turn off", "stan
by". You scroll with the joystick, and press to select
-You can run and control more than 10 different popular programme
from the cellphone. The most controllable is the popular music an
video player "winamp version 2 and 5"
I have several songs and DivX movies in an external 120GB US
harddrive, organised in playlists: frank sinatra, julio iglesias
celine dion, adult movies, action movies, etc..
On the cellphone accessory menu, I select FMA, winamp, selec
playlist, action movies, I am presented with the list of action movies
in my playlist (all this appear on the cellphone!), select "terminator
3", and it starts playing on my 17 inches flat screen computer monitor.
The same for music. You can select to turn "shuffle" and "repeat" on
and off from the phone.
You can off course play, pause, select previous or next track.
You can change the volume, and see the volume slider move left and
right on winamp.

I can control WinDVD, turn subtitles on and off, full screen on and
off, select a chapter, change the volume.

With bluetooth, all this can be done while you are not in the same
room with the computer. This is real, I am doing it everyday.

I am sure I didn't mention all the nice things one can do with FMA.
Visit the FMA forum and learn to merge different scripts. You just need
to know how to copy and paste.

What's the name of 'that' software package that you can get for a windows PC
that gives an on-screen display/alert when your bluetooth attached T610 is
ringing?

I saw the software in operation on a PC when I attended a recent exhibition
but forgot to to talk to the exhibitor about it.

Also what's the best freeware you can get for a PC to allow you to send SMS
messages via a PC/bluetooth/T610 connection?
-----------------

FMA, more than likely, on sourceforge

Try this VisualGSM Lite, it's Windows based and freeware - 'SMS Gateway
(http://www.visualtron.com)