Digital meat thermometer that does not cause juice losses
While I heartily recommend a remote probe thermometer that you can leave in your meat and have a readout outside of the oven, it is only for convenience. Piercing the meat with a thermometer (or fork, etc) isn't going to cause any significant loss of juice. You may rupture a couple of cells right where the thermometer went in, but that's it. Your meat isn't just a water-balloon of juices waiting to be popped, so you needn't worry.

Myth: Never use a fork to turn meat

Is it ok to probe my meat?