Just found this. With lots of interest in iPhone style color meters, this looks like it can use your existing X-Rite style display calibration meter, and an Android tablet to capture the complete spectrum of on-set lighting. Very useful for accurate white balance. (.44 lighting is discussed)

http://www.argyllcms.com/pro/index.html
http://www.argyllcms.com

Tri-stimulus & Spectral measurement in Emissive, Ambient, Reflective, Transmissive & Flash measurement modes. Display Refresh rate.

Chromaticity and Spectral graphic display.

Configurable readouts of any measurement combination.

Current measurement, reference measurement and White, Black, Red, Yellow, Green Cyan, Blue and Magenta Primary measurement registers. CIE XYZ based tri-stimulus colorspaces: XYZ, Yxy, Yu'v', Lab*, LChab, Luv, LCh*uv & DIN99 Lab. Component differences between the Reference and the Measurement CIE XYZ based tri-stimulus colorspaces. Delta E between Reference and the Measurement: CIE Delta E 76, CIE Delta E 94,CIE Delta E 94 Textile, IE Delta E 2000, CMC Delta E 2:1, CMC Delta E 1:1, DIN99 Delta E. Density: Visual Density, Status A Density, Status M Density, Status T Density, Status E (DIN) Density, ISO Type 1 & 2 Density. Photography specific: Incident illuminance, reflected luminance, flash measurement, Exposure Value (EV), Interactive Exposure Calculator. Color Temperature, Delta Color Temperature, Black Body or Daylight, Correlated or DE2000, Kelvin or Mired. Configurable RGB colorspace including BT.709, BT.2020, DCI-P3, custom, BT.1886, Delta RGB, RGB or CMY Adjustment Direction. Color Rendering Index (CIE 1995 Ra + R9), Television Lighting Consistency Index (EBU TLCI-2012 Qa) Visual Contrast ARPANSA UV Exposure Web RGB, Visual Compare Swatches, Named Color, Named Color Visual Swatch, with installable CxF or ICC Palettes. Save and Restore ColorMeter and Instrument configurations.

Instruments supported: JETI specbos: 1211 & 1201 Image Engineering EX1 Klein: K1, K8, K10, K10-A X-Rite: DTP20, DTP94, ColorMunki Design or Photo, ColorMunki Create or Smile, Eye-One Display Pro, ColorMunki Display, OEM i1d3 instruments, Eye-One Pro2 Gretag-Macbeth: Eye-One Pro, Eye-One Monitor, Eye-One Display 1 or 2 or LT, HP DreamColor or APS, CalMAN X2, Huey Sequel Imaging: MonacoOPTIX Lacie Blue Eye DataColor: Spyder 2, Spyder 3, Spyder 4 & Spyder 5 SwatchMate Cube, with improved color accuracy. Video Test Pattern Generator (TPG) Capability: By making use of a ChromeCast, ColorMeter can act as an HDMI Video Test Patch and Test Card source. While the ChromeCast is not a bit perfect TPG, the use of dithering makes it accurate to within perceptual limits. It can be used to display one of six standard Test Cards, covering Display geometry, Probe locations, Low clipping, High clipping, Neutrals and Color ramps. It can also be used to display a test patch color that matches the reference RGB value Readout, which combined with continuous measurement mode and Delta E and RGB adjustment Readouts, gives color by color Video calibration capability. System Requirements: USB On The Go (OTG) capable Android tablet or phone.
Recommended screen size of 94 mm (3.7 inches) or greater. Android V4.0 (Ice Cream Sandwich) or later. USB OTG adapter lead. BlueTooth LE for connecting with SwatchMate Cube via Bluetooth.

The exact capabilities depend on the type of instrument you are using.

Current price looks like $99 so not cheep, but much cheeper than buying custom iPhone light meter, or dedicated light meter. Also you may already own the hardware for other calibration purposes!