Cold feet is more than merely a malady that affects those about to hit the karaoke stage. It's a real problem for those of us who love the snow but who hate it when our lower extremities go completely numb—for me a product of extreme height and abnormally low blood pressure.
Various foot-warming systems have been around for decades. The first portable chemical warmers date to at least 1910, and not a lot has changed since then. Activated by air or powered by liquid fuel, these warmers often feel scorching hot for a few hours, then barely lukewarm for the rest of the day.
Lately, battery technology has come to the world of portable warmers, giving them a more consistent discharge and better reusability.
ThermaCell's ProFlex Heavy Duty heated insoles should be fairly self-explanatory, and the pair of ProFlex inserts feature a thick sole with a heating element embedded inside. A slim battery, padded on one side, slides into the spot where your heel goes. When you're out of juice, both batteries slip into a USB-powered recharger. The whole affair is operated via Bluetooth, courtesy of a rudimentary smartphone app.
For reasonably chilly toes, the system works better than I'd expected. While the three heat levels promise temperatures ranging from 100 to 115 degrees Fahrenheit, in reality all three levels tend to hover around 90 to 95. This is far from scorching, but plenty warm if the ambient temperature is at or around freezing—enough to keep feet toasty without getting all sweaty. Heat is reasonably well dispersed, but it's hottest around the ball of the foot.
While the ProFlex solves some of the problems of chemical handwarmers, its myriad downsides create a few more.
First is fit. While you can trim the length of the insoles, the pad is extremely thick, and I had trouble finding a boot where it would fit comfortably, without feeling cramped and without popping my heel out of the back of the shoe each time I took a step. Battery life is promised at up to 8.5 hours, but I only managed about half that on a mix of high and low heat levels. Strangely, the battery on the right foot died a full half hour before the one on the left. An even bigger issue: Though the battery was dead, the app still indicated it had 60 percent of its juice remaining.
That error aside, ProFlex's app is rough and half-baked, and the Bluetooth implementation on the soles is exceptionally short in range. (For best results hold your phone right next to your shoe when changing temperatures.) ProFlex does at least link the two soles together for you, though, so while you can control foot temperature independently, you don't have to.
Then there's the price tag. At $199, this is rarified air in a world of $3-a-pair chemical warmers. But frankly, if I could get them to fit better in my boots, I wouldn't really mind. Buggy apps can be fixed. Frostbite, not so much.
6/10 - A solid product with some issues.
