Hello lo2e - I hope still in time for your mid-March plans.

HotelRatePRO at https://www.hotelratepro.com
does exactly what you are looking for.

We offer Hotel Rate Tracking for booked and un-booked hotels, with an option for BrandSearch - track same brand hotels near the booked/requested hotel.

You can select Member-Only rates or Public rates, and Refundable or Non-Refundable rates.

We send you a RateAlert as soon as a lower rate is found.
For booked hotels you can specify a minimum price-drop, so we do not send you a RateAlert for a small drop in price.

We also offer tracking for a Sold-Out Hotel for any room availability, with an option of BrandSearch.

We currently support the 48 brands of Hilton, IHG, Marriott and Starwood. Hyatt brands will be added this month, followed by Wyndham (top brands) and Best Western.
We plan to support additional hotel groups and offer additional services.

Thank you - HotelRatePRO Representative.