And now for the choices....

AiM
Motec
Traqmate 
Video V-Box
Race Keeper
CDS
RLC  
ChaseCam  
Pi
Stack
Racepak
Race Technology
Bosch
Rumble Strip Racing     
GPX Pro 
Petrel Data (SoloStorm)
RaceCapture
Magni-Tech 
McLaren Electronics
Gem Electronics
EFI Technologies
2D 
BJR Technologies

Smart Phone Based Systems

Harry's Lap Timer
Trackmaster
Torque
RaceChrono
RageTank  (app download)
CMS Lap Timer Pro
Wifi Lapper 
Track Attack 

And some Suppliers

Euroamerican Engineering (Magneti Marelli)
Auto-Ware (Systems, Sensors, Engineering, Coacing)

Active Sensors (Sensors)
Ashcroft (Pressure Sensors)
VariOhm Eurosensor (Sensors)
KA Sensors (Sensors)
Position Sensors (Linear and Rotary Sensors)
Instrumentation Sensors Inc (Sensors)
Raetech (Load Cells)
Gill Sensors (Sensors)
Texense (Sensors)
Penny and Giles (Sensors)
Measurement Specialties (Sensors)
McLaren Electronics (Sensors)
Magni-Tec (Sensors)
Omega (Bare Strain Gauges and Load Cells)
Sensor-Technik UK (sensors)
First Sensors (IR Temp Sensors)
Smith Systems (Hall Effect Sensors)
Therma Motorsports (Temp Sensors)
Prag (Torque, Bending, Angle, Position Sensors)
Straintek (Bondable and Bolt on Strain Gauges)
Semip (Position Sensors and Potentiometers)
Position Sensors (Linear and Rotary Sensors)
PCB Sensors (Accelerometers, Force, and Pressure Sensors)
NovaTech (Loadcells)
Opitel-Thevon (Optical Speed Sensors)
Mag Canica (Torque Sensing)
Kulite (Pressure Transducers)
BF1 Systems (TPMS and Load Cells)
Kistler (Cylinder Pressure Sensors)
UniMeasure (string pots)
Celesco (linear, rotary, and string sensors)
The Sensor Connection (thermocouples)
Reventec (position and torque sensors)