You want to get it through a reputable mortgage lender. I'd be very worried about the fine print. The AARP has good advice on this.
In general it seems like a good idea. You've spent your life building up equity in the house. You might as well spend that money, but you don't want to move. So you sell your house to the bank, who has a contract to let you live there as long as you want. (That's why you'd better make sure it's a good lender, who's not going to screw you at a bad time.)
If you don't want to sell the house to the bank, you can take a Home Equity Loan, which is similar: they loan you the money in exchange for a lien on your house. With the home equity loan you have to keep making mortgage payments, and with the reverse mortgage they just send you money. The Home Equity Loan requires a lot more management on your part, but you keep owning your house. The loan eventually has to be paid off, and that usually comes when they sell the house. If they live a long time... well, that can become a problem.
Shop around for the cheapest reverse mortgage. There can be considerable up-front costs and you want to minimize those.
Once you've got it all set up, though, your parents get their money and can really enjoy their retirement.
Of course every dollar they spend is money you don't get in inheritance, but I say, good for them. Blow the wad. You only live once.